VANGUARD INSTITUTIONAL INDEX FUND
N-30D, 2000-08-30
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VANGUARD(R) INSTITUTIONAL INDEX FUND
June 30, 2000

SEMIANNUAL

[GRAPHIC]
[THE VANGUARD GROUP(R) LOGO]

<PAGE>
HAVE THE PRINCIPLES OF INVESTING CHANGED?
     In a world of frenetic  change in business,  technology,  and the financial
markets,  it is natural to wonder whether the basic principles of investing have
changed.
     We don't think so.
     The most  successful  investors  over the coming  decade  will be those who
began the new century with a fundamental  understanding  of risk and who had the
discipline to stick with long-term investment programs.
     Certainly,  investors  today  confront a challenging,  even  unprecedented,
environment.  Valuations of market  indexes are at or near historic  highs.  The
strength and duration of the bull market in U.S.  stocks have inflated  people's
expectations  and  diminished  their  recognition  of the market's  considerable
risks. And the incredible  divergence in stock returns--many  technology-related
stocks  gained  100% or more in 1999,  yet prices fell for more than half of all
stocks--has made some investors question the idea of diversification.
     And then there is the  Internet.  Undeniably,  it is a powerful  medium for
communications and transacting business.  For investors,  the Internet is a vast
source  of  information  about  investments,  and  online  trading  has  made it
inexpensive and convenient to trade stocks and invest in mutual funds.
     However,  new tools do not guarantee good  workmanship.  Information is not
the same as wisdom.  Indeed,  much of the information,  opinion,  and rumor that
swirl  about  financial  markets  each day  amounts  to  "noise"  of no  lasting
significance.  And the fact  that  rapid-fire  trading  is easy does not make it
beneficial.   Frequent  trading  is  almost  always  counterpro-ductive  because
costs--even at low commission rates--and taxes detract from the returns that the
markets  provide.  Sadly,  many  investors jump into a "hot" mutual fund just in
time to see it  cool  off.  Meanwhile,  long-term  fund  investors  are  hurt by
speculative  trading  activity  because they bear part of the costs  involved in
accommodating purchases and redemptions.
     Vanguard  believes that  intelligent  investors  should  resist  short-term
thinking and focus instead on a few time-tested principles:
     * Invest for the long term.  Pursuing your  long-term  investment  goals is
more like a marathon than a sprint.
     * Diversify  your  investments  with  holdings in stocks,  bonds,  and cash
investments.  Remember that, at any moment, some part of a diversified portfolio
will lag other  parts,  and be wary of taking on more risk by "piling  onto" the
best-performing  part of your holdings.  Today's leader could well be tomorrow's
laggard.
     * Step back from the daily  frenzy of the  markets;  focus on your  overall
asset allocation.
     * Capture as much of the market's  return as possible by  minimizing  costs
and taxes.  Costs and taxes  diminish  long-term  returns while doing nothing to
reduce the risks you incur as an investor.

--------------------------------------------------------------------------------
CONTENTS

REPORT FROM THE CHAIRMAN .......1        PERFORMANCE SUMMARIES ..........8
THE MARKETS IN PERSPECTIVE .....4        FINANCIAL STATEMENTS ...........9
FUND PROFILE ...................6
--------------------------------------------------------------------------------

All  comparative  mutual fund data are from Lipper  Inc. or  Morningstar,  Inc.,
unless  otherwise  noted.   "Standard  &  Poor's(R),"  "S&P(R),"  "S&P  500(R),"
"Standard & Poor's 500," and "500" are trademarks of The McGraw-Hill  Companies,
Inc. Frank Russell Company is the owner of trademarks and copyrights relating to
the Russell  Indexes.  "Wilshire  5000(R)" and "Wilshire 4500" are trademarks of
Wilshire Associates Incorporated.

<PAGE>
1

REPORT FROM THE CHAIRMAN
[PHOTO]
John J. Brennan

The U.S. stock market endured a choppy six months during the first half of 2000,
as many  investors  struggled to sort out the  implications  of rising  interest
rates,  strong economic growth,  and the sky-high  valuations of some technology
companies.
     In this challenging environment, Vanguard Institutional Index Fund provided
a total  return of -0.4% for the six months  ended  June 30.  The fund's  return
matched that of its target benchmark,  the Standard & Poor's 500 Index, but fell
short of the 1.3% return of the average large- capitalization core mutual fund.
------------------------------------------------------
                                       TOTAL RETURNS
                                     SIX MONTHS ENDED
                                      JUNE 30, 2000
------------------------------------------------------
Vanguard Institutional Index Fund           -0.4%
------------------------------------------------------
Average Large-Cap Core Fund*                 1.3%
------------------------------------------------------
S&P 500 Index                               -0.4%
------------------------------------------------------
Plus Shares                                 -0.4%
------------------------------------------------------
*Derived from data provided by Lipper Inc.

     The adjacent  table  compares the fund's  six-month  total return  (capital
change plus reinvested  dividends) with the returns of the S&P 500 Index and our
average peer. The performance of the fund's Plus Shares, which are available for
a minimum  investment of $200 million,  is presented at the bottom of the table.
Vanguard  Institutional  Index Fund's return is based on a decrease in net asset
value from $134.02 per share on December 31, 1999,  to $132.85 per share on June
30, 2000, and is adjusted for distributions  totaling $0.680 per share paid from
net  investment  income.  (For the Plus  Shares,  the total return is based on a
decrease in net asset  value from  $134.02 per share to $132.86 per share and is
adjusted for distributions totaling $0.702 per share.)

THE PERIOD IN REVIEW
The first half of 2000 was a tumultuous  time in the  financial  markets,  which
were buffeted by a complex set of crosscurrents.  The domestic economy continued
to grow at a strong pace: The production of goods and services during the second
quarter of 2000 was about 6% higher  than in the same  period  last  year,  even
after adjusting for  inflation.Unemployment  remained low, hovering around 4% of
the workforce.  Elsewhere in the world,  growth was picking up from more subdued
levels.
     Economic  growth is generally  good for corporate  earnings and,  thus, for
stock  prices.  But investors  and economic  policymakers  have worried that the
combination of rapid economic growth and low unemployment  would trigger sharply
higher wages and inflation.  The Federal Reserve Board, in an effort to slow the
economy's  momentum and forestall an inflationary  outburst,  continued to raise
short-term  interest rates during the half-year.  The Fed boosted its target for
the federal funds rate three times by a total of 1.0 percentage point (100 basis
points).  In all,  the Fed has raised its target rate by 175 basis points in the
past 12 months.
     For most of the first  quarter of 2000,  a  continuing  boom in  technology
stocks kept the market  averages  rising,  despite the threat of higher interest
rates. But during the second quarter,  tech stocks in particular cooled off. The
market may have reacted to evidence that the ideal  combination  of rapid growth
and low  inflation  was coming to an end.  If the Fed  succeeds  in slowing  the
economy,  corporate  earnings  growth might slow,  too.  And if earnings  growth
slowed, some investors reasoned, technology and

<PAGE>
2

telecommunications  stocks  would  have a tough  time  maintaining  their  lofty
price/earnings  multiples. The split between the two quarters was evident in the
results for the  tech-dominated  Nasdaq Composite Index, which rose 12.7% in the
first quarter,  only to slide -14.7% in the second.  End result?  A -3.9% return
for the half-year.
     The overall  U.S.  stock  market,  as measured by the  Wilshire  5000 Total
Market Index,  posted a -0.7% return for the six months.  The small-cap  Russell
2000 Index gained 3.0%,  outpacing  the  large-cap  Standard & Poor's 500 Index,
which posted a negative return of -0.4%. Leadership within the market during the
period switched back and forth between growth  stocks-those whose prices reflect
high expectations for future profitability-and value stocks, whose low prices in
relation to earnings,  book value, and dividends  reflect lower  expectations by
the market.  Growth  stocks were in front early on, but value  stocks  performed
best in late March and April. Growth issues bounced back in June,  however,  and
for the full six months,  growth  generally  outpaced  value.  For example,  the
growth stocks within the Russell 1000 Index  (comprising  the 1,000 largest U.S.
stocks) earned 4.2%, while the value stocks declined by an equal amount.
     The Fed's efforts  succeeded in pushing up short-term  interest rates:  The
yield of 3-month  U.S.  Treasury  bills  climbed 52 basis  points (from 5.33% to
5.85%)  during the  half-year.  But after rising  early in the year,  yields for
longer-term  Treasuries began to fall after the Treasury announced that it would
use rising  federal  budget  surpluses to buy back billions of dollars' worth of
long-term bonds. A shrinking supply of long-term  Treasuries caused their prices
to rise and their yields to fall. By June 30, the 30-year  Treasury bond's yield
had  fallen  58 basis  points,  from  6.48% to  5.90%.  Yields  on  high-quality
corporate  bonds were flat to slightly  higher.  But for  low-quality  corporate
("junk") bonds, prices fell and yields rose as investors worried about increased
defaults.

PERFORMANCE OVERVIEW
As you should expect, Vanguard Institutional Index Fund earned a return that was
in line with the market segment in which it invests,  namely  large-cap  stocks.
However,  as the previous table  indicates,  our fund did not keep pace with its
average peer.
         Your fund  registered a return of -0.4% during the half-year,  an exact
match with its target index but a good deal short of the average  return of 1.3%
earned by large-cap core mutual funds.  Our shortfall versus our average peer is
owed largely to the  generally  lackluster  performance  of several of the large
companies that dominate the index but whose returns were  generally  outpaced by
companies further down the  capitalization  ladder. The index's relatively heavy
weighting  in larger  companies  can work in our fund's favor in relation to our
actively  managed  competitors  when the largest  companies are powering the S&P
500's  performance-as they did for the past several years.  However, it can work
to our detriment when smaller-cap stocks lead the market, as they did during the
past six months.
     Over  the  past  several  years,   technology   companies  have  played  an
increasingly  large role in the S&P 500 Index, and their performance has set the
pace for the index. During the half-year,  much of the volatility in the S&P 500
Index was attributed to tech shares,  which constituted an average of nearly 28%
of the index in the period.  The  technology  sector posted a return of 4.6% for
the six months, while the overall index returned -0.4%. Two of the other largest
sectors  within the S&P 500  registered  negative  returns:  financial  services
shares declined -0.1% and consumer  discretionary  companies-a category composed
mainly of  retailers-returned  -15.9%.  Among the bright  spots were health care
stocks,  which gained 23.4%, and "other energy" companies,  which benefited from
higher oil prices and rose 34.4% as a group.

<PAGE>
3

     We again  point out that the S&P 500 Index is a good  measure of  large-cap
stocks but does not represent the entire U.S. stock market. In fact, the S&P 500
excludes about 6,400 stocks that total about 21% of the value of the U.S. equity
market. To gain exposure to mid- and small-cap stocks that the S&P 500 excludes,
an investor  must look to an index that  captures the entire  market or to those
that specifically target smaller companies.
     It's worth  noting that  matching  the return of an  unmanaged  index is no
small feat. All mutual funds incur operating expenses and  administrative  costs
that indexes,  which are  theoretical  constructs,  do not bear. Our low expense
ratio-just  0.06% of average net assets,  or 60 cents for every $1,000  invested
(0.025% for Plus  Shares)-helps  keep our returns  closely in line with those of
our target  indexes.  (By way of comparison,  the average  large-cap core mutual
fund  levies an expense  ratio of 1.31%,  or $13.10 per  $1,000  invested.)  And
Vanguard Quantitative Equity Group, which provides investment management for all
of  Vanguard's  index funds,  offset the effects of our costs  through  skillful
portfolio management. When reviewing our performance,  keep in mind that our low
costs provide our funds, and thus our  shareholders,  with a powerful  advantage
over long periods,  but they do not guarantee  superior  performance  during all
periods.

IN SUMMARY
During  the  first  half of 2000,  we  witnessed  very  sharp  day-to-day  price
fluctuations in the stock market,  significant swings in investor sentiment, and
sudden shifts in market leadership. All of this volatility, squeezed into a mere
six months,  underscored the fact that unpredictability is par for the course in
financial  markets.  The  timing,  extent,  and  duration of such  episodes  are
impossible to foretell with  precision,  but investors must be willing to endure
them to reap the long-term rewards of investing.
     At Vanguard,  we reiterate our long-standing  recommendation for navigating
stormy seas toward long-term  financial goals.  First, create an investment plan
with a balance of stock funds, bond funds, and money market funds suited to your
time horizon,  investment  objectives,  and  tolerance for market  fluctuations.
Then, once you have such a diversified  plan in place,  stick with it. Avoid the
impulse  to  alter it based on  short-term  events-whether  those be  unsettling
turbulence in the market or glittery returns from some particular  corner of the
market. "Stay the course" is timeless investment wisdom.

/S/ John J. Brennan
John J. Brennan
Chairman and Chief Executive Officer        July 18, 2000


IN MEMORY

It is with  great  sadness  that I  report  the  death  of John C.  Sawhill,  an
independent  trustee of the fund and a member of The Vanguard  Group's  board of
directors  since 1991.  John, an economist who was president and chief executive
officer  of The  Nature  Conservancy,  died on May 18 at age 63. He was a senior
lecturer at the Harvard  Business School and had formerly served as president of
New York  University  and as deputy  secretary of the U.S.  Department of Energy
under President Jimmy Carter.  John was a remarkable man who was full of energy,
vigor,  and life. His experience and wisdom added a great deal to Vanguard,  and
his death is a blow to everyone  who knew and loved him.  Though  John's work on
behalf of our funds was often  carried on behind the scenes,  he was a dedicated
advocate for the best interests of our shareholders. He will be missed.

<PAGE>
4

THE MARKETS IN PERSPECTIVE
SIX MONTHS ENDED JUNE 30, 2000

The  perpetual  tug-of-war in the  financial  markets ended in a near  stalemate
during the first  half of 2000,  despite  lots of  back-and-forth  movement.  On
average,  neither  stock nor bond  prices  ended the  period far from where they
began it. However,  bonds,  thanks to their superior income,  outpaced stocks in
total return.
     Economic  signals were  conflicting.  Growth continued at a rapid pace, and
corporate  profits  rose  smartly.  On the other hand,  stock prices as the year
began already  reflected  high levels of optimism,  and the market  administered
severe punishment to companies that failed to live up to earnings  expectations.
Also weighing on the market were concerns that the economy's  vigor at a time of
low  unemployment  would  inevitably  push labor costs and other prices  higher.
Indeed,  higher  costs for oil and natural gas pushed  broad gauges of inflation
higher (the Consumer Price Index gained 2.4% for the six months and 3.7% for the
twelve months ended June 30). Yet core inflation, which excludes energy and food
items, registered a moderate 2.4% gain during the 12 months ended June 30.
     The  Federal  Reserve  Board  raised  short-term  interest  rates  by  0.25
percentage  point in February  and again in March,  before  adding a  half-point
boost in May.  These  steps,  which  followed  three  quarter-  percentage-point
increases  in  1999,  took  the  Fed's  target  for  short-term  rates  to 6.5%.
Thereafter,  signs of a slowing in economic activity cropped up, although it was
not certain that the Fed was done trying to throttle down the economic engine.

--------------------------------------------------------------------------------
                                                        TOTAL RETURNS
                                                  PERIODS ENDED JUNE 30, 2000
                                              ----------------------------------
                                              6 MONTHS      1 YEAR      5 YEARS*
--------------------------------------------------------------------------------
STOCKS
  S&P 500 Index                                 -0.4%        7.2%        23.8%
  Russell 2000 Index                             3.0        14.3         14.3
  Wilshire 5000 Index                           -0.7        10.0         22.6
  MSCI EAFE Index                               -4.0        17.4         11.6
--------------------------------------------------------------------------------
BONDS
  Lehman Aggregate Bond Index                    4.0%        4.6%         6.3%
  Lehman 10 Year Municipal Bond Index            4.0         4.5          6.0
  Salomon Smith Barney 3--Month
    U.S. Treasury Bill Index                     2.8         5.3          5.2
--------------------------------------------------------------------------------
OTHER
  Consumer Price Index                           2.4%        3.7%         2.5%
--------------------------------------------------------------------------------
*Annualized.


U.S. STOCK MARKETS
Stock prices were quite  volatile  during the  half-year,  and large  day-to-day
price  fluctuations  in market  averages were  commonplace.  There also were two
swift  shifts in market  leadership.  The year began with a  continuance  in the
rapid rise for the "TMT" stocks  (technology,  media,  telecommunications)  that
were the market's darlings during 1999.  Through  mid-March,  the surge in these
"new economy"  groups left "old  economy"  stocks far behind.  For example,  the
Nasdaq Composite Index, which is dominated by tech-related stocks,  gained 15.6%
and the Russell 1000 Value Index fell -10.4% during January and February. But in
mid-March,  value  stocks took charge and TMT stocks  slumped.  The Russell 1000
Value Index returned 12.1% while the Nasdaq  plummeted to a -27.4% return in the
March-May period. But June brought another  flip-flop:  The value index declined
-4.6%, while the Nasdaq rebounded with a 14.5% return.

<PAGE>
5

     When the half-year was over, most broad market indexes had modest declines.
The all-market Wilshire 5000 Index returned -0.7%, the  large-capitalization S&P
500 Index slipped  -0.4%,  and the Nasdaq fell -3.9%.  Small- and mid-cap stocks
did better:  The small-cap  Russell 2000 Index gained 3.0% and the Wilshire 4500
Completion  Index,  comprising  virtually all the U.S. stocks outside of the S&P
500, eked out a 0.3% return.

U.S. BOND MARKETS
The Federal  Reserve  most  directly  influences  interest  rates of  short-term
securities.  The Fed  pushed  up its  target  federal  funds  rate  (charged  on
overnight  loans  between  banks) by 1 percentage  point to 6.5%.  But yields of
3-month U.S.  Treasury bills rose only half as far (0.52 percentage point, or 52
basis  points to 5.85%).  And yields  actually  declined on  long-term  Treasury
securities,  whose  prices  rose.  Big federal  budget  surpluses  are causing a
shrinking  supply of Treasury bonds.  The 10-year  Treasury note's yield fell 41
basis  points  to 6.03% as of June 30,  and the  yield of the  30-year  Treasury
declined 58 basis points-from 6.48% to 5.90%-during the half-year.
     The  upshot  was an  unusual  "inversion"  in the yield  curve.  Instead of
sloping  upward-with  yields  increasing  along with the  maturity  of  Treasury
securities-the curve descended. The 5.90% yield of 30-year Treasuries on June 30
was 49 basis points below the 6.39% yield on 3-year Treasury notes.
     Corporate bonds did not perform as well as Treasuries for two main reasons:
a record level of new offerings and investors' concern that credit quality might
be  declining.  The  rise  in  yields  (and  fall  in  prices)  was  slight  for
higher-quality  corporate  bonds but more severe for  high-yield  "junk"  bonds.
Investors grew wary of riskier bonds due to an increase in defaults.  The Lehman
High  Yield Bond  Index saw a price  decline  of -5.7%  during the first half of
2000, more than offsetting its six-month  income of 4.5%.  Tax-exempt  municipal
bonds  generally  outperformed  corporates  but did  not do as well as  Treasury
securities. The overall taxable bond market, as measured by the Lehman Aggregate
Bond  Index,  returned  4.0%,  as a price gain of 0.4%  augmented  a 3.6% income
return.

INTERNATIONAL STOCK MARKETS
International  stock markets were generally  unprofitable for U.S. investors due
to lack- luster local market  performances and a stronger U.S. dollar during the
half-year.   Although   economic  growth  in  most  of  Europe  appeared  to  be
strengthening, stocks were hurt by continued economic weakness in Japan and from
expectations of higher interest rates. On the other hand,  European stock prices
got some support from an increase in corporate takeovers.
     In local currencies,  European stocks posted a 1.7% return in the aggregate
and stocks from the Pacific region recorded a modest decline of -2.6%.  However,
the dollar's strength diminished those results for U.S. investors,  for whom the
Morgan Stanley Capital  International (MSCI) Europe Index returned -3.0% and the
MSCI Pacific Free Index returned -5.9%. The MSCI Europe,  Australasia,  Far East
(EAFE) Index of  developed  foreign  markets  registered a -4.0% return for U.S.
investors.
     The Select Emerging Markets Free Index fell -9.6% in U.S.  dollars,  having
declined  -3.5% in local  currencies.  The  index was hit by  weakness  in South
Africa (-15%) and several emerging Asian markets,  including  Indonesia  (-44%),
Thailand (-36%),  and the Philippines  (-36%).  The biggest gains among emerging
markets were in Israel (+27%) and Venezuela (+19%).

<PAGE>
6

FUND PROFILE
INSTITUTIONAL INDEX FUND

This Profile  provides a snapshot of the fund's  characteristics  as of June 30,
2000,  compared where appropriate to its unmanaged target index. Key elements of
this Profile are defined on page 7.

PORTFOLIO CHARACTERISTICS
-------------------------------------------------------
                            INSTITUTIONAL
                                    INDEX       S&P 500
-------------------------------------------------------
Number of Stocks                      514           500
Median Market Cap                  $94.9B        $94.9B
Price/Earnings Ratio                28.7x         28.7x
Price/Book Ratio                     5.2x          5.2x
Yield                                1.1%          1.1%
Yield--Plus Shares                   1.1%          1.1%
Return on Equity                    24.5%         24.5%
Earnings Growth Rate                17.3%         17.3%
Foreign Holdings                     1.2%          1.2%
Turnover Rate                        11%*            --
Expense Ratio                      0.06%*            --
Expense Ratio--
 Plus Shares                      0.025%*            --
Cash Investments                     0.0%            --

*Annualized.


INVESTMENT FOCUS
------------------
MARKET CAP - LARGE
STYLE - BLEND


VOLATILITY MEASURES
-------------------------------------------------------
                            INSTITUTIONAL
                                    INDEX       S&P 500
-------------------------------------------------------
R-Squared                            1.00          1.00
Beta                                 1.00          1.00


TEN LARGEST HOLDINGS
(% OF TOTAL NET ASSETS)
------------------------------------------
General Electric Co.                  4.2%
Intel Corp.                           3.6
Cisco Systems, Inc.                   3.5
Microsoft Corp.                       3.3
Pfizer, Inc.                          2.4
Exxon Mobil Corp.                     2.2
Wal-Mart Stores, Inc.                 2.0
Oracle Corp.                          1.9
Citigroup, Inc.                       1.6
Nortel Networks Corp.                 1.6
------------------------------------------
Top Ten                              26.3%


SECTOR DIVERSIFICATION (% OF COMMON STOCKS)
----------------------------------------------------------------------
                              JUNE 30, 1999          JUNE 30, 2000
                        ----------------------------------------------
                              INSTITUTIONAL   INSTITUTIONAL
                                  INDEX           INDEX       S&P 500
----------------------------------------------------------------------
Auto & Transportation ........     2.5%            1.6%          1.6%
Consumer Discretionary .......    12.8            11.8          11.8
Consumer Staples .............     7.8             5.7           5.7
Financial Services ...........    16.5            13.4          13.4
Health Care ..................    11.1            11.7          11.7
Integrated Oils ..............     5.4             4.5           4.5
Other Energy .................     1.1             1.8           1.8
Materials & Processing .......     3.7             2.2           2.2
Producer Durables ............     4.1             2.9           2.9
Technology ...................    18.4            29.9          29.9
Utilities ....................    11.3             8.6           8.6
Other ........................     5.3             5.9           5.9
----------------------------------------------------------------------

<PAGE>
7

BETA. A measure of the magnitude of a fund's past  share-price  fluctuations  in
relation  to the ups and downs of the  overall  market  (or  appropriate  market
index).  The market (or index) is assigned a beta of 1.00, so a fund with a beta
of 1.20  would have seen its share  price  rise or fall by 12% when the  overall
market rose or fell by 10%.

CASH  INVESTMENTS.  The  percentage  of a fund's  net assets  invested  in "cash
equivalents"-highly liquid, short-term, interest-bearing securities. This figure
does  not  include  cash  invested  in  futures   contracts  to  simulate  stock
investment.

EARNINGS  GROWTH RATE.  The average  annual rate of growth in earnings  over the
past five years for the stocks now in a fund.

EXPENSE  RATIO.  The  percentage of a fund's  average net assets used to pay its
annual  administrative  and advisory  expenses.  These expenses  directly reduce
returns to investors.

FOREIGN HOLDINGS. The percentage of a fund's equity assets represented by stocks
or American Depositary Receipts of companies based outside the United States.

INVESTMENT  FOCUS.  This  grid  indicates  the  focus  of a fund in terms of two
attributes:  market  capitalization  (large,  medium,  or  small)  and  relative
valuation  (growth,  value, or a blend).

MEDIAN  MARKET  CAP.  An  indicator  of the  size of  companies  in which a fund
invests;  the  midpoint  of  market   capitalization   (market  price  x  shares
outstanding) of a fund's stocks, weighted by the proportion of the fund's assets
invested  in each  stock.  Stocks  representing  half of the fund's  assets have
market capitalizations above the median, and the rest are below it.

NUMBER OF STOCKS. An indicator of diversification. The more stocks a fund holds,
the more  diversified  it is and the more  likely  to  perform  in line with the
overall stock market.

PRICE/BOOK  RATIO.  The share price of a stock divided by its net worth, or book
value,  per share.  For a fund,  the weighted  average  price/book  ratio of the
stocks it holds.

PRICE/EARNINGS  RATIO.  The ratio of a stock's  current  price to its  per-share
earnings over the past year. For a fund, the weighted  average P/E of the stocks
it holds. P/E is an indicator of market expectations about corporate  prospects;
the higher the P/E, the greater the expectations for a company's future growth.

R-SQUARED.  A measure of how much of a fund's past  returns can be  explained by
the returns from the overall market (or its benchmark  index). If a fund's total
return  were  precisely  synchronized  with the  overall  market's  return,  its
R-squared  would  be 1.00.  If a  fund's  returns  bore no  relationship  to the
market's returns, its R-squared would be 0.

RETURN ON  EQUITY.  The annual  average  rate of return  generated  by a company
during the past five years for each dollar of  shareholder's  equity (net income
divided by  shareholder's  equity).  For a fund, the weighted  average return on
equity for the companies whose stocks it holds.

SECTOR DIVERSIFICATION. The percentages of a fund's common stocks that come from
each of the major  industry  groups that compose the stock  market.

TEN LARGEST  HOLDINGS.  The percentage of net assets that a fund has invested in
its ten largest holdings.  (The average for stock mutual funds is about 35%.) As
this percentage  rises, a fund's returns are likely to be more volatile  because
they are more dependent on the fortunes of a few companies.

TURNOVER RATE. An indication of trading  activity during the period.  Funds with
high  turnover  rates  incur  higher  transaction  costs and are more  likely to
distribute capital gains (which are taxable to investors).

YIELD.  A snapshot of a fund's  income from interest and  dividends.  The yield,
expressed  as a  percentage  of the fund's net asset  value,  is based on income
earned over the past 30 days and is  annualized,  or  projected  forward for the
coming  year.  The  index  yield  is  based on the  current  annualized  rate of
dividends paid on stocks in the index.

<PAGE>
8

PERFORMANCE SUMMARIES

All of the data on this page represent past performance, which cannot be used to
predict  future returns that may be achieved by the fund.  Note,  too, that both
share  price and  return  can  fluctuate  widely.  An  investor's  shares,  when
redeemed, could be worth more or less than their original cost.

INSTITUTIONAL INDEX FUND
TOTAL INVESTMENT RETURNS: JULY 31, 1990-JUNE 30, 2000
--------------------------------------------------------
         INSTITUTIONAL INDEX FUND    S&P 500
FISCAL   CAPITAL  INCOME   TOTAL      TOTAL
YEAR     RETURN   RETURN   RETURN     RETURN
--------------------------------------------------------
1990     -7.3%    1.6%     -5.7%      -5.7%
1991     26.4     3.9      30.3       30.5
1992      4.5     3.0       7.5        7.6
1993      7.1     2.9      10.0       10.1
1994     -1.5     2.8       1.3        1.3
1995     34.4     3.2      37.6       37.6
--------------------------------------------------------

--------------------------------------------------------
         INSTITUTIONAL INDEX FUND    S&P 500
FISCAL   CAPITAL  INCOME   TOTAL      TOTAL
YEAR     RETURN   RETURN   RETURN     RETURN
--------------------------------------------------------
1996     20.6%    2.5%     23.1%      23.0%
1997     31.2     2.2      33.4       33.4
1998     27.1     1.7      28.8       28.6
1999     19.7     1.5      21.2       21.0
2000*    -0.9     0.5      -0.4       -0.4
--------------------------------------------------------
*Six months ended June 30, 2000.
See  Financial  Highlights  table  on page 17 for  dividend  and  capital  gains
information for the past five years.


INSTITUTIONAL INDEX FUND PLUS SHARES
TOTAL INVESTMENT RETURNS: JULY 7, 1997-JUNE 30, 2000
--------------------------------------------------------
         INSTITUTIONAL INDEX FUND
             PLUS SHARES             S&P 500
FISCAL   CAPITAL  INCOME   TOTAL      TOTAL
YEAR     RETURN   RETURN   RETURN     RETURN
--------------------------------------------------------
1997      6.2%    1.1%      7.3%       7.3%
1998     27.1     1.7      28.8       28.6
--------------------------------------------------------

--------------------------------------------------------
         INSTITUTIONAL INDEX FUND
             PLUS SHARES             S&P 500
FISCAL   CAPITAL  INCOME   TOTAL      TOTAL
YEAR     RETURN   RETURN   RETURN     RETURN
--------------------------------------------------------
1999     19.7%    1.5%     21.2%      21.0%
2000*    -0.9     0.5      -0.4       -0.4
--------------------------------------------------------
*Six months ended June 30, 2000.
See  Financial  Highlights  table  on page 18 for  dividend  and  capital  gains
information since inception.


AVERAGE ANNUAL TOTAL RETURNS: PERIODS ENDED JUNE 30, 2000
--------------------------------------------------------------------------------
                                                            SINCE INCEPTION
                          INCEPTION                     ------------------------
                            DATE      1 YEAR   5 YEARS   CAPITAL  INCOME   TOTAL
--------------------------------------------------------------------------------
Institutional Index Fund   7/31/1990    7.42%   23.91%   15.41%   2.61%   18.02%
Institutional Index Fund
   Plus Shares             7/7/1997     7.47     --       7.10    1.65    18.75
--------------------------------------------------------------------------------

<PAGE>
9

FINANCIAL STATEMENTS
JUNE 30, 2000 (UNAUDITED)

STATEMENT OF NET ASSETS
This Statement  provides a detailed list of the fund's holdings,  including each
security's market value on the last day of the reporting period.  Securities are
grouped and  subtotaled by asset type (common  stocks,  bonds,  etc.),  with the
fund's S&P 500 Index  common  stocks  listed in  descending  market value order.
Other assets are added to, and  liabilities  are  subtracted  from, the value of
Total  Investments to calculate the fund's Net Assets.  Finally,  Net Assets are
divided by the  outstanding  shares of the fund to arrive at its share price, or
Net Asset Value (NAV) Per Share.
     At the end of the Statement of Net Assets, you will find a table displaying
the  composition  of the fund's net assets.  Because all income and any realized
gains must be  distributed  to  shareholders  each year,  the bulk of net assets
consists of Paid in Capital (money invested by shareholders).  The amounts shown
for  Undistributed  Net  Investment  Income and  Accumulated  Net Realized Gains
usually   approximate   the  sums  the  fund  had  available  to  distribute  to
shareholders as income  dividends or capital gains as of the statement date, but
may  differ  because  certain   investments  or  transactions   may  be  treated
differently  for  financial  statement  and tax purposes.  Any  Accumulated  Net
Realized Losses,  and any cumulative excess of distributions  over net income or
net realized gains, will appear as negative  balances.  Unrealized  Appreciation
(Depreciation)  is the  difference  between  the  market  value  of  the  fund's
investments  and their  cost,  and  reflects  the gains  (losses)  that would be
realized if the fund were to sell all of its investments at their statement-date
values.

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------
                                                                              MARKET
                                                                              VALUE*
INSTITUTIONAL INDEX FUND                                   SHARES              (000)
-------------------------------------------------------------------------------------
COMMON STOCKS (99.6%)(1)
-------------------------------------------------------------------------------------
<S>                                                  <C>                <C>
     General Electric Co.                              29,026,553         $1,538,407
     Intel Corp.                                        9,825,672          1,313,570
o    Cisco Systems, Inc.                               20,408,704          1,297,228
o    Microsoft Corp.                                   15,439,533          1,235,163
     Pfizer, Inc.                                      18,467,699            886,450
     Exxon Mobil Corp.                                 10,213,400            801,752
     Wal-Mart Stores, Inc.                             13,067,738            753,028
o    Oracle Corp.                                       8,327,658            700,044
     Citigroup, Inc.                                    9,901,093            596,541
     Nortel Networks Corp.                              8,685,281            592,770
     International Business
          Machines Corp.                                5,201,419            569,880
     Lucent Technologies, Inc.                          9,553,979            566,073
     American International
          Group, Inc.                                   4,522,273            531,367
     Merck & Co., Inc.                                  6,746,347            516,939
o    EMC Corp.                                          6,366,431            489,817
     SBC Communications Inc.                            9,980,387            431,652
o    Sun Microsystems, Inc.                             4,654,434            423,263
     The Coca-Cola Co.                                  7,256,937            416,820
     Johnson & Johnson                                  4,080,740            415,725
     Royal Dutch Petroleum
          Co. ADR                                       6,286,985            387,043
o    WorldCom, Inc.                                     8,400,042            385,352
o    Dell Computer Corp.                                7,554,817            372,547
     Hewlett-Packard Co.                                2,934,261            366,416
o    America Online, Inc.                               6,735,827            355,315
     Home Depot, Inc.                                   6,783,175            338,735
     Bristol-Myers Squibb Co.                           5,787,465            337,120
     Eli Lilly & Co.                                    3,313,387            330,925
     Texas Instruments, Inc.                            4,801,079            329,774
o    Viacom Inc. Class B                                4,435,229            302,427
     AT&T Corp.                                         9,280,362            293,491
     Time Warner, Inc.                                  3,860,279            293,381
     Morgan Stanley Dean
          Witter & Co.                                  3,320,682            276,447
     The Walt Disney Co.                                6,096,161            236,607
     BellSouth Corp.                                    5,516,628            235,146
     Tyco International Ltd.                            4,952,474            234,623
     Bell Atlantic Corp.                                4,534,801            230,425
     American Home Products Corp.                       3,826,451            224,804
     Procter & Gamble Co.                               3,837,216            219,681
     Corning, Inc.                                        809,227            218,390
     Schering-Plough Corp.                              4,293,957            216,845
o    Applied Materials, Inc.                            2,367,676            214,571
o    Amgen, Inc.                                        3,012,466            211,626
     Bank of America Corp.                              4,862,246            209,077
     American Express Co.                               3,916,819            204,164
     Abbott Laboratories                                4,542,821            202,439
o    Yahoo!, Inc.                                       1,592,809            197,309
     Pharmacia Corp.                                    3,724,064            192,488
     PepsiCo, Inc.                                      4,227,815            187,874
     Motorola, Inc.                                     6,314,558            183,517
     Wells Fargo Co.                                    4,727,177            183,178
     Philip Morris Cos., Inc.                           6,704,460            178,087
     GTE Corp.                                          2,824,676            175,836
     Medtronic, Inc.                                    3,511,619            174,923
     The Chase Manhattan Corp.                          3,628,514            167,138
     Chevron Corp.                                      1,912,825            162,231
     U S WEST, Inc.                                     1,867,674            160,153
o    Sprint PCS                                         2,669,582            158,840
     Fannie Mae                                         2,955,606            154,246
     Ford Motor Co.                                     3,536,240            152,058
</TABLE>

<PAGE>
10

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------
                                                                              MARKET
                                                                              VALUE*
INSTITUTIONAL INDEX FUND                                   SHARES              (000)
-------------------------------------------------------------------------------------
<S>                                                    <C>               <C>
o    Micron Technology, Inc.                            1,626,748         $  143,255
     Enron Corp.                                        2,146,292            138,436
o    NEXTEL Communications, Inc.                        2,223,407            136,045
     E.I. du Pont de Nemours & Co.                      3,072,766            134,434
     Charles Schwab Corp.                               3,992,452            134,246
     Sprint Corp.                                       2,571,883            131,166
     Merrill Lynch & Co., Inc.                          1,137,289            130,788
o    QUALCOMM, Inc.                                     2,172,642            130,359
     McDonald's Corp.                                   3,920,397            129,128
     Compaq Computer Corp.                              4,981,764            127,346
     Schlumberger Ltd.                                  1,669,614            124,595
o    MediaOne Group, Inc.                               1,820,132            120,700
o    Broadcom Corp.                                       515,900            112,950
     The Boeing Co.                                     2,659,699            111,209
o    Veritas Software Corp.                               977,092            110,427
     Gillette Co.                                       3,062,659            107,002
     Colgate-Palmolive Co.                              1,691,842            101,299
     The Bank of New York Co., Inc.                     2,162,441            100,553
     Anheuser-Busch Cos., Inc.                          1,325,479             98,997
     Automatic Data Processing, Inc.                    1,838,945             98,498
o    Comcast Corp.-Special Class A                      2,413,580             97,750
o    Agilent Technologies, Inc.                         1,325,295             97,741
     Minnesota Mining &
          Manufacturing Co.                             1,161,227             95,801
o    Siebel Systems, Inc.                                 585,264             95,727
     Walgreen Co.                                       2,955,023             95,115
     Kimberly-Clark Corp.                               1,630,124             93,528
     General Motors Corp.                               1,569,652             91,138
     FleetBoston Financial Corp.                        2,644,013             89,896
     Bank One Corp.                                     3,362,594             89,319
     Computer Associates
          International, Inc.                           1,726,526             88,377
     Texaco Inc.                                        1,619,637             86,246
o    ADC Telecommunications, Inc.                         985,256             82,638
     Freddie Mac                                        2,038,291             82,551
     Marsh & McLennan Cos., Inc.                          790,398             82,547
o    Tellabs, Inc.                                      1,201,441             82,224
     United Technologies Corp.                          1,380,448             81,274
     Honeywell International Inc.                       2,341,779             78,889
o    Analog Devices, Inc.                               1,037,347             78,838
     The Gap, Inc.                                      2,496,430             78,013
o    Xilinx, Inc.                                         941,994             77,773
     Target Corp.                                       1,337,883             77,597
     Emerson Electric Co.                               1,251,140             75,538
o    Clear Channel
          Communications, Inc.                            993,706             74,528
     The Seagram Co. Ltd.                               1,279,568             74,215
     Alcoa Inc.                                         2,535,020             73,516
o    Solectron Corp.                                    1,749,202             73,248
     Unilever NV ADR                                    1,675,858             72,062
o    Network Appliance, Inc.                              892,948             71,882
     First Union Corp.                                  2,874,865             71,333
o    Global Crossing Ltd.                               2,585,611             68,034
o    Safeway, Inc.                                      1,456,392             65,720
     MBNA Corp.                                         2,350,779             63,765
     Halliburton Co.                                    1,301,629             61,421
     Duke Energy Corp.                                  1,078,102             60,778
     First Data Corp.                                   1,209,603             60,027
     Firstar Corp.                                      2,845,990             59,944
     Baxter International, Inc.                           851,656             59,882
     Dow Chemical Co.                                   1,983,486             59,876
     Cardinal Health, Inc.                                807,221             59,734
o    Altera Corp.                                         583,700             59,501
o    3Com Corp.                                         1,029,274             59,312
     Linear Technology Corp.                              912,152             58,321
     Household International, Inc.                      1,387,276             57,659
     Fifth Third Bancorp                                  908,259             57,447
     ALLTEL Corp.                                         924,349             57,252
o    AES Corp.                                          1,249,703             57,018
o    Seagate Technology Inc.                            1,028,620             56,574
     Electronic Data Systems Corp.                      1,366,652             56,374
o    Maxim Integrated Products, Inc.                      828,674             56,298
     Bestfoods                                            804,971             55,744
     Eastman Kodak Co.                                    908,860             54,077
o    The Kroger Co.                                     2,449,811             54,049
     Williams Cos., Inc.                                1,296,126             54,032
     Gateway, Inc.                                        943,551             53,547
o    Kohl's Corp.                                         956,424             53,201
     Mellon Financial Corp.                             1,441,207             52,514
     J.P. Morgan & Co., Inc.                              476,022             52,422
     Illinois Tool Works, Inc.                            884,659             50,426
     State Street Corp.                                   471,706             50,030
o    Apple Computer, Inc.                                 954,355             49,984
     HCA-The Healthcare Co.                             1,634,962             49,662
     Sara Lee Corp.                                     2,549,516             49,238
o    LSI Logic Corp.                                      900,055             48,715
     Allstate Corp.                                     2,184,663             48,609
     Associates First Capital Corp.                     2,135,537             47,649
     Gannett Co., Inc.                                    781,418             46,739
     Omnicom Group Inc.                                   521,191             46,419
     Washington Mutual, Inc.                            1,606,054             46,375
     Lowe's Cos., Inc.                                  1,121,680             46,059
     CVS Corp.                                          1,144,723             45,789
     Paychex, Inc.                                      1,089,352             45,753
     Adobe Systems, Inc.                                  351,001             45,630
     H.J. Heinz Co.                                     1,033,445             45,213
     Conoco Inc. Class B                                1,830,392             44,959
     CIGNA Corp.                                          477,436             44,640
o    Guidant Corp.                                        899,141             44,507
     American General Corp.                               728,266             44,424
     Southern Co.                                       1,901,742             44,334
     Costco Wholesale Corp.                             1,309,918             43,227
     U.S. Bancorp                                       2,204,367             42,434
     Northern Trust Corp.                                 651,795             42,407
     International Paper Co.                            1,417,316             42,254
o    Comverse Technology, Inc.                            447,727             41,639
     Albertson's, Inc.                                  1,242,103             41,300
     Sysco Corp.                                          976,928             41,153
     UnitedHealth Group Inc.                              476,220             40,836
     Xerox Corp.                                        1,954,730             40,561
     SunTrust Banks, Inc.                                 886,744             40,513
     PE Corp.-PE Biosystems Group                         610,731             40,232
     PNC Financial Services Group                         851,487             39,913
     Coastal Corp.                                        627,611             38,206
     Interpublic Group of Cos., Inc.                      884,630             38,039
o    Best Buy Co., Inc.                                   599,299             37,906
     Phillips Petroleum Co.                               744,305             37,727
     Providian Financial Corp.                            418,053             37,625
o    Teradyne, Inc.                                       507,769             37,321
o    MedImmune Inc.                                       498,124             36,861
o    Sanmina Corp.                                        430,004             36,765
o    Computer Sciences Corp.                              490,906             36,665
</TABLE>

<PAGE>
11

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------
                                                                              MARKET
                                                                              VALUE*
INSTITUTIONAL INDEX FUND                                   SHARES              (000)
-------------------------------------------------------------------------------------
<S>                                                   <C>                 <C>
     Campbell Soup Co.                                  1,238,790         $   36,080
     AFLAC, Inc.                                          778,287             35,753
     Kellogg Co.                                        1,189,917             35,400
     The Hartford Financial Services
          Group Inc.                                      630,457             35,266
     Scientific-Atlanta, Inc.                             465,890             34,709
o    Advanced Micro Devices, Inc.                         449,176             34,699
     Caterpillar, Inc.                                  1,022,069             34,623
     Waste Management, Inc.                             1,822,193             34,622
     El Paso Energy Corp.                                 678,471             34,560
     Carnival Corp.                                     1,772,193             34,558
     Harley-Davidson, Inc.                                890,094             34,269
     Sears, Roebuck & Co.                               1,033,702             33,725
     Lehman Brothers Holdings, Inc.                       354,337             33,507
     Transocean Sedco Forex Inc.                          617,082             32,975
     General Mills, Inc.                                  854,643             32,690
o    FedEx Corp.                                          850,098             32,304
     Wachovia Corp.                                       593,618             32,204
     NIKE, Inc. Class B                                   802,280             31,941
o    KLA-Tencor Corp.                                     545,305             31,934
     The Chubb Corp.                                      512,967             31,547
     Baker Hughes, Inc.                                   968,795             31,001
     Conexant Systems, Inc.                               637,239             30,986
     Avon Products, Inc.                                  696,103             30,977
     Tribune Co.                                          882,585             30,890
     The Clorox Co.                                       688,212             30,840
     The McGraw-Hill Cos., Inc.                           570,248             30,793
     General Dynamics Corp.                               588,338             30,741
     National City Corp.                                1,777,472             30,328
     Pitney Bowes, Inc.                                   756,172             30,247
     Dominion Resources, Inc.                             697,827             29,919
o    National Semiconductor Corp.                         517,606             29,374
     Weyerhaeuser Co.                                     683,025             29,370
o    Cendant Corp.                                      2,095,218             29,333
     Lockheed Martin Corp.                              1,173,540             29,118
     Kansas City Southern
          Industries, Inc.                                326,896             28,992
     The Quaker Oats Co.                                  383,838             28,836
     Burlington Northern
          Santa Fe Corp.                                1,255,726             28,803
     Allergan, Inc.                                       379,960             28,307
o    Biogen, Inc.                                         435,342             28,080
     American Electric Power
          Co., Inc.                                       943,872             27,962
     PG&E Corp.                                         1,129,727             27,820
     Molex, Inc.                                          575,194             27,681
     Southwest Airlines Co.                             1,454,897             27,552
     ConAgra, Inc.                                      1,443,260             27,512
     The Limited, Inc.                                  1,259,616             27,239
     Union Pacific Corp.                                  726,650             27,022
     Wrigley, (Wm.) Jr. Co.                               334,610             26,832
     Aetna Inc.                                           413,522             26,543
o    Boston Scientific Corp.                            1,195,381             26,224
o    BMC Software, Inc.                                   716,388             26,137
     RadioShack Corp.                                     547,237             25,925
     FPL Group, Inc.                                      522,724             25,875
     Reliant Energy, Inc.                                 867,444             25,644
     Capital One Financial Corp.                          574,569             25,640
o    Lexmark International Group,
          Inc. Class A                                    379,218             25,502
     Deere & Co.                                          686,681             25,407
     Marriott International, Inc.
          Class A                                         702,523             25,335
     Nabisco Group Holdings Corp.                         957,136             24,826
o    Tenet Healthcare Corp.                               917,615             24,776
     BB&T Corp.                                         1,021,975             24,400
     Burlington Resources, Inc.                           631,597             24,159
     Dover Corp.                                          595,212             24,143
     Delphi Automotive
          Systems Corp.                                 1,651,765             24,054
     Masco Corp.                                        1,314,047             23,735
     Unocal Corp.                                         712,488             23,601
     May Department Stores Co.                            974,931             23,398
     Aon Corp.                                            750,200             23,303
     Textron, Inc.                                        423,048             22,977
     USX-Marathon Group                                   913,382             22,892
     TXU Corp.                                            773,281             22,812
     Occidental Petroleum Corp.                         1,080,813             22,765
     PPG Industries, Inc.                                 510,896             22,639
     KeyCorp                                            1,275,632             22,483
     Avery Dennison Corp.                                 328,856             22,074
     Rohm & Haas Co.                                      638,222             22,019
     Public Service Enterprise
          Group, Inc.                                     634,329             21,964
     Franklin Resources Corp.                             714,546             21,704
o    Staples, Inc.                                      1,403,279             21,575
     Becton, Dickinson & Co.                              740,634             21,247
     St. Paul Cos., Inc.                                  622,137             21,230
o    Federated Department
          Stores, Inc.                                    627,882             21,191
     Barrick Gold Corp.                                 1,159,068             21,081
     Air Products & Chemicals, Inc.                       672,803             20,731
o    Novellus Systems, Inc.                               365,987             20,701
     Comerica, Inc.                                       458,957             20,596
     Danaher Corp.                                        415,414             20,537
     Lincoln National Corp.                               562,466             20,319
     Unicom Corp.                                         521,304             20,168
     Coca-Cola Enterprises, Inc.                        1,233,810             20,127
     Newell Rubbermaid, Inc.                              781,410             20,121
     PECO Energy Corp.                                    497,144             20,041
     Edison International                                 974,265             19,972
     Alcan Aluminium Ltd.                                 641,493             19,886
     Circuit City Stores, Inc.                            596,588             19,799
     New York Times Co. Class A                           498,624             19,696
     Apache Corp.                                         333,373             19,606
     Hershey Foods Corp.                                  402,411             19,517
     Union Carbide Corp.                                  393,487             19,478
     PaineWebber Group, Inc.                              426,955             19,426
o    American Power
          Conversion Corp.                                470,161             19,188
     Ingersoll-Rand Co.                                   474,849             19,113
     Dow Jones & Co., Inc.                                259,955             19,042
     Golden West Financial Corp.                          463,499             18,917
     Dollar General Corp.                                 964,911             18,816
     Anadarko Petroleum Corp.                             375,762             18,530
o    Sapient Corp.                                        172,619             18,459
     Consolidated Edison Inc.                             621,843             18,422
     Entergy Corp.                                        674,752             18,345
     AmSouth Bancorp                                    1,152,673             18,155
     Delta Air Lines, Inc.                                359,069             18,155
</TABLE>

<PAGE>
12

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------
                                                                              MARKET
                                                                              VALUE*
INSTITUTIONAL INDEX FUND                                   SHARES              (000)
-------------------------------------------------------------------------------------
<S>                                                  <C>                 <C>
o    Convergys Corp.                                      345,328         $   17,914
     Ralston-Ralston Purina Group                         893,614             17,816
o    ALZA Corp.                                           300,950             17,794
     Rockwell International Corp.                         551,689             17,378
     Loews Corp.                                          289,181             17,351
     Archer-Daniels-Midland Co.                         1,766,660             17,335
     Praxair, Inc.                                        462,556             17,317
     McKesson HBOC, Inc.                                  826,640             17,308
     SLM Holding Corp.                                    459,140             17,189
     Jefferson-Pilot Corp.                                302,486             17,072
     Norfolk Southern Corp.                             1,124,037             16,720
     TJX Cos., Inc.                                       880,091             16,502
     Mattel, Inc.                                       1,246,744             16,441
     Amerada Hess Corp.                                   265,806             16,414
o    Starbucks Corp.                                      427,975             16,343
     Union Pacific Resources
          Group, Inc.                                     739,504             16,269
     Kerr-McGee Corp.                                     275,994             16,266
     Progressive Corp. of Ohio                            214,334             15,861
     Raytheon Co. Class B                                 823,358             15,850
     FirstEnergy Corp.                                    677,430             15,835
     IMS Health, Inc.                                     871,959             15,695
     TRW, Inc.                                            361,593             15,684
     Columbia Energy Group                                236,550             15,524
o    Watson Pharmaceuticals, Inc.                         282,244             15,171
     T. Rowe Price                                        354,313             15,058
     CP&L, Inc.                                           468,323             14,957
o    Bed Bath & Beyond, Inc.                              411,702             14,924
     Ecolab, Inc.                                         380,378             14,859
     Cincinnati Financial Corp.                           472,110             14,842
     Synovus Financial Corp.                              828,507             14,602
     Tiffany & Co.                                        212,506             14,344
     Constellation Energy Group                           438,907             14,292
     Eaton Corp.                                          213,317             14,292
     UnumProvident Corp.                                  705,436             14,153
     Charter One Financial                                614,411             14,131
     MGIC Investment Corp.                                310,502             14,128
     J.C. Penney Co., Inc.                                765,234             14,109
     Fort James Corp.                                     603,681             13,960
     MBIA, Inc.                                           288,457             13,900
     Ameren Corp.                                         402,559             13,586
     CSX Corp.                                            640,890             13,579
     Florida Progress Corp.                               288,799             13,537
     Dun & Bradstreet Corp.                               472,855             13,535
     Northrop Grumman Corp.                               204,279             13,533
     Bear Stearns Co., Inc.                               324,543             13,509
o    Cabletron Systems, Inc.                              534,762             13,503
o    PeopleSoft, Inc.                                     801,245             13,421
o    Unisys Corp.                                         913,012             13,296
o    Wellpoint Health Networks Inc.
          Class A                                         182,090             13,190
     Georgia Pacific Group                                500,291             13,133
     Biomet, Inc.                                         336,193             12,922
     Johnson Controls, Inc.                               251,554             12,908
     Regions Financial Corp.                              646,919             12,858
o    Sealed Air Corp.                                     245,479             12,857
o    Mercury Interactive Corp.                            132,315             12,801
     DTE Energy Co.                                       418,529             12,791
     Summit Bancorp                                       515,772             12,701
     Vulcan Materials Co.                                 295,550             12,616
o    Tricon Global Restaurants, Inc.                      432,533             12,219
     Knight Ridder                                        227,835             12,118
     Bausch & Lomb, Inc.                                  155,700             12,047
     Tosco Corp.                                          423,200             11,982
     Young & Rubicam Inc.                                 208,287             11,911
     Cinergy Corp.                                        466,305             11,862
     CenturyTel, Inc.                                     411,431             11,829
o    AMR Corp.                                            439,174             11,611
     Harcourt General, Inc.                               210,318             11,436
o    St. Jude Medical, Inc.                               245,915             11,281
     Parker Hannifin Corp.                                328,453             11,250
     SouthTrust Corp.                                     492,999             11,154
     Union Planters Corp.                                 396,999             11,091
o    Compuware Corp.                                    1,056,909             10,965
     Equifax, Inc.                                        414,170             10,872
o    NCR Corp.                                            279,137             10,869
     Brown-Forman Corp. Class B                           200,968             10,802
     Sabre Holdings Corp.                                 378,450             10,786
     Old Kent Financial Corp.                             402,932             10,778
     Eastman Chemical Co.                                 224,992             10,743
     The BFGoodrich Co.                                   314,708             10,720
     Fortune Brands, Inc.                                 464,519             10,713
     Newmont Mining Corp.                                 492,348             10,647
     Genuine Parts Co.                                    518,492             10,370
     Huntington Bancshares Inc.                           651,285             10,298
o    Citrix Systems, Inc.                                 542,791             10,279
     Tektronix, Inc.                                      138,798             10,271
o    Ceridian Corp.                                       424,886             10,224
     New Century Energies, Inc.                           339,720             10,192
     Sempra Energy                                        599,256             10,187
     Sherwin-Williams Co.                                 480,480             10,180
     Hilton Hotels Corp.                                1,080,559             10,130
     Countrywide Credit
          Industries, Inc.                                332,255             10,071
     Millipore Corp.                                      133,123             10,034
     Whirlpool Corp.                                      214,144              9,984
     Black & Decker Corp.                                 249,794              9,820
o    Thermo Electron Corp.                                457,342              9,633
     GPU, Inc.                                            355,695              9,626
o    Kmart Corp.                                        1,410,308              9,608
     Nordstrom, Inc.                                      394,950              9,528
     Leggett & Platt, Inc.                                576,419              9,511
     Dana Corp.                                           446,997              9,471
     PerkinElmer, Inc.                                    142,386              9,415
     H & R Block, Inc.                                    288,621              9,344
     Conseco Inc.                                         954,313              9,305
     Northern States Power Co.                            460,948              9,305
     Torchmark Corp.                                      375,964              9,282
     PPL Corp.                                            422,490              9,268
o    Toys R Us, Inc.                                      634,436              9,239
     The Goodyear Tire & Rubber Co.                       458,760              9,175
     Placer Dome, Inc.                                    958,209              9,163
     International Flavors &
          Fragrances, Inc.                                301,698              9,107
     PACCAR, Inc.                                         224,508              8,910
o    Parametric Technology Corp.                          809,762              8,907
     Cooper Industries, Inc.                              273,240              8,897
o    Novell, Inc.                                         959,995              8,880
     Willamette Industries, Inc.                          324,992              8,856
o    AutoZone Inc.                                        392,468              8,634
</TABLE>

<PAGE>
13

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------
                                                                              MARKET
                                                                              VALUE*
INSTITUTIONAL INDEX FUND                                   SHARES              (000)
-------------------------------------------------------------------------------------
<S>                                                  <C>                <C>
     Phelps Dodge Corp.                                   231,009         $    8,591
     Mallinckrodt, Inc.                                   197,058              8,560
o    Comcast Corp. Class A                                218,396              8,490
     Maytag Corp.                                         229,790              8,473
     W.W. Grainger, Inc.                                  274,485              8,458
     Pinnacle West Capital Corp.                          248,629              8,422
     Nucor Corp.                                          249,484              8,280
o    Rowan Cos., Inc.                                     271,684              8,252
o    Inco Ltd.                                            532,721              8,191
o    HEALTHSOUTH Corp.                                  1,130,823              8,128
     R.R. Donnelley & Sons Co.                            357,650              8,069
     VF Corp.                                             335,024              7,978
o    Andrew Corp.                                         236,400              7,934
     ITT Industries, Inc.                                 257,953              7,835
     Sunoco, Inc.                                         259,629              7,643
o    US Airways Group, Inc.                               195,430              7,622
     The Mead Corp.                                       301,385              7,610
     Hasbro, Inc.                                         505,015              7,607
o    Harrah's Entertainment, Inc.                         358,562              7,507
     SAFECO Corp.                                         374,415              7,441
     SuperValu Inc.                                       385,725              7,353
     Sigma-Aldrich Corp.                                  250,069              7,315
     Westvaco Corp.                                       294,575              7,309
     Ashland, Inc.                                        207,104              7,262
     C.R. Bard, Inc.                                      148,019              7,123
     CMS Energy Corp.                                     321,736              7,118
     Fluor Corp.                                          224,089              7,087
o    Niagara Mohawk Holdings Inc.                         505,360              7,043
     UST, Inc.                                            475,576              6,985
o    Adaptec, Inc.                                        304,969              6,938
     Pall Corp.                                           362,741              6,711
     Adolph Coors Co. Class B                             107,637              6,512
     Temple-Inland Inc.                                   153,849              6,462
     Engelhard Corp.                                      372,539              6,356
     The Stanley Works                                    256,921              6,102
     Winn-Dixie Stores, Inc.                              423,666              6,064
     Wendy's International, Inc.                          333,500              5,940
     Autodesk, Inc.                                       171,009              5,932
     Darden Restaurants Inc.                              362,816              5,896
o    Office Depot, Inc.                                   927,757              5,798
     Shared Medical Systems Corp.                          79,335              5,786
     Liz Claiborne, Inc.                                  160,159              5,646
     Crown Cork & Seal Co., Inc.                          375,823              5,637
o    Navistar International Corp.                         181,410              5,635
o    Visteon Corp.                                        463,076              5,615
o    Allied Waste Industries, Inc.                        553,484              5,535
     Homestake Mining Co.                                 762,815              5,244
     Bemis Co., Inc.                                      153,596              5,165
o    FMC Corp.                                             89,019              5,163
     Great Lakes Chemical Corp.                           159,685              5,030
o    Owens-Illinois, Inc.                                 429,711              5,022
     Meredith Corp.                                       148,476              5,011
     Eastern Enterprises                                   79,368              5,000
     Deluxe Corp.                                         212,087              4,997
     Alberto-Culver Co. Class B                           163,416              4,994
     Rite Aid Corp.                                       758,907              4,980
     USX-U.S. Steel Group                                 259,092              4,809
o    Quintiles Transnational Corp.                        337,889              4,773
     Snap-On Inc.                                         171,813              4,575
     NICOR, Inc.                                          136,282              4,446
     Allegheny Technologies Inc.                          244,055              4,393
     Hercules, Inc.                                       312,259              4,391
     Boise Cascade Corp.                                  167,828              4,343
     Crane Co.                                            177,587              4,318
     Brunswick Corp.                                      257,809              4,270
     Centex Corp.                                         174,026              4,090
o    Pactiv Corp.                                         495,725              3,904
o    Consolidated Stores, Inc.                            325,172              3,902
     Tupperware Corp.                                     169,275              3,724
o    Freeport-McMoRan Copper &
          Gold Inc. Class B                               396,688              3,669
     American Greetings Corp.
          Class A                                         189,252              3,596
     Dillard's Inc.                                       274,556              3,363
     Peoples Energy Corp.                                 103,581              3,353
     Raytheon Co. Class A                                 171,471              3,333
     The Timken Co.                                       178,860              3,331
     Louisiana-Pacific Corp.                              305,430              3,322
     Cummins Engine Co., Inc.                             121,613              3,314
     Ryder System, Inc.                                   174,172              3,298
     Thomas & Betts Corp.                                 169,811              3,248
     Ball Corp.                                            87,224              2,808
     Potlatch Corp.                                        84,075              2,785
     Kaufman & Broad Home Corp.                           137,751              2,729
     Worthington Industries, Inc.                         252,906              2,656
o    Reebok International Ltd.                            165,545              2,638
     Pulte Corp.                                          120,844              2,613
     Longs Drug Stores, Inc.                              115,395              2,510
o    Viacom Inc. Class A                                   36,030              2,464
     Cooper Tire & Rubber Co.                             216,567              2,409
o    W.R. Grace & Co.                                     197,645              2,396
o    Humana, Inc.                                         491,217              2,395
     Polaroid Corp.                                       131,421              2,374
     National Service Industries, Inc.                    119,291              2,326
     Briggs & Stratton Corp.                               65,478              2,243
     ONEOK, Inc.                                           85,460              2,217
o    Manor Care, Inc.                                     300,085              2,101
     Russell Corp.                                         95,265              1,905
     Great Atlantic & Pacific Tea
          Co., Inc.                                       112,337              1,868
     Armstrong Holdings, Inc.                             117,929              1,806
     Springs Industries Inc. Class A                       52,512              1,680
     McDermott International, Inc.                        174,486              1,538
     Owens Corning                                        160,882              1,488
o    Bethlehem Steel Corp.                                386,305              1,376
o    MIPS Technologies, Inc. Class B                       34,355              1,323
o    Qwest Communications
          International Inc.                               13,620                677
     IKON Office Solutions, Inc.                          171,644                665
o    Freeport-McMoRan Copper &
          Gold, Inc. Class A                               72,417                661
     NACCO Industries, Inc. Class A                        16,656                585
o    Silicon Graphics, Inc.                               114,911                431
     Milacron Inc.                                          5,348                 78
-------------------------------------------------------------------------------------
TOTAL COMMON STOCKS
(COST $22,735,898)                                                        36,829,833
-------------------------------------------------------------------------------------
</TABLE>

<PAGE>
14

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------
                                                             FACE             MARKET
                                                           AMOUNT             VALUE*
INSTITUTIONAL INDEX FUND                                    (000)              (000)
-------------------------------------------------------------------------------------
TEMPORARY CASH INVESTMENTS (0.2%)(1)
-------------------------------------------------------------------------------------
<S>                                                     <C>             <C>
Federal Home Loan Mortgage Corp.
(2)  6.25%, 7/27/2000                                    $  3,000        $     2,986
Federal National Mortgage Assn.
(2)  6.06%, 7/13/2000                                       8,000              7,986
(2)  6.454%, 8/3/2000                                       4,000              3,976
REPURCHASE AGREEMENTS
Collateralized by U.S. Government
     Obligations in a Pooled
     Cash Account
     6.71%, 7/3/2000                                       61,422             61,422
     6.71%, 7/3/2000--Note E                                9,469              9,469
-------------------------------------------------------------------------------------
TOTAL TEMPORARY CASH INVESTMENTS
(COST $85,838)                                                                85,839
-------------------------------------------------------------------------------------
TOTAL INVESTMENTS (99.8%)
(COST $22,821,736)                                                        36,915,672
-------------------------------------------------------------------------------------
OTHER ASSETS AND LIABILITIES (0.2%)
-------------------------------------------------------------------------------------
Other Assets                                                                 568,922
Liabilities--Note E                                                         (493,705)
                                                                         ------------
                                                                              75,217
-------------------------------------------------------------------------------------
NET ASSETS (100%)                                                        $36,990,889
=====================================================================================
</TABLE>

 * See Note A in Notes to Financial Statements.
 o Non-income-producing security.
(1)The fund invests a portion of its cash reserves in equity markets through the
   use of index futures contracts.  After giving  effect to futures investments,
   the fund's effective  common stock  and  temporary cash investment  positions
   represent 100.2% and -0.4%, respectively,  of net assets. See Note D in Notes
   to Financial Statements.
(2)Securities  with an aggregate  value of  $14,948,000  have been segregated as
   initial margin for open futures contracts.
ADR--American Depositary Receipt.


--------------------------------------------------------------------------------
                                                                         AMOUNT
                                                                          (000)
--------------------------------------------------------------------------------
AT JUNE 30, 2000, NET ASSETS CONSISTED OF:
--------------------------------------------------------------------------------
Paid in Capital--Note C                                             $23,146,600
Undistributed Net Investment Income                                       9,195
Accumulated Net
   Realized Losses--Note C                                             (253,923)
Unrealized Appreciation
   (Depreciation)--Note D
   Investment Securities                                             14,093,936
   Futures Contracts                                                     (4,919)
--------------------------------------------------------------------------------
NET ASSETS                                                          $36,990,889
================================================================================

Institutional Shares--Net Assets
Applicable to 223,137,592 outstanding $.001
   par value shares of beneficial interest
   (unlimited authorization)                                        $29,644,343
--------------------------------------------------------------------------------
NET ASSET VALUE PER SHARE-
   INSTITUTIONAL SHARES                                                 $132.85
================================================================================

Plus Shares-Net Assets
Applicable to 55,295,792 outstanding $.001
   par value shares of beneficial interest
   (unlimited authorization)                                         $7,346,546
--------------------------------------------------------------------------------
NET ASSET VALUE PER SHARE-
     PLUS SHARES                                                        $132.86
================================================================================

<PAGE>
15

STATEMENT OF OPERATIONS
This Statement  shows dividend and interest income earned by the fund during the
reporting  period,  and details the operating  expenses charged to each class of
its shares.  These  expenses  directly  reduce the amount of  investment  income
available to pay to shareholders as dividends. This Statement also shows any Net
Gain (Loss) realized on the sale of investments, and the increase or decrease in
the Unrealized Appreciation  (Depreciation) on investments during the period. If
the fund invested in futures  contracts during the period,  the results of these
investments are shown separately.

--------------------------------------------------------------------------------
                                                        INSTITUTIONAL INDEX FUND
                                                  SIX MONTHS ENDED JUNE 30, 2000
                                                                           (000)
--------------------------------------------------------------------------------
INVESTMENT INCOME
INCOME
    Dividends                                                          $203,483
    Interest                                                              3,658
    Security Lending                                                        406
                                                                     -----------
        Total Income                                                    207,547
                                                                     -----------
EXPENSES
    The Vanguard Group--Note B
        Management and Administrative-Institutional Shares                8,679
        Management and Administrative-Plus Shares                           834
                                                                     -----------
        Total Expenses                                                    9,513
--------------------------------------------------------------------------------
NET INVESTMENT INCOME                                                   198,034
--------------------------------------------------------------------------------
REALIZED NET GAIN (LOSS)
    Investment Securities Sold                                          308,990
    Futures Contracts                                                    (5,705)
--------------------------------------------------------------------------------
REALIZED NET GAIN                                                       303,285
--------------------------------------------------------------------------------
CHANGE IN UNREALIZED APPRECIATION (DEPRECIATION)
    Investment Securities                                              (602,911)
    Futures Contracts                                                    (6,103)
--------------------------------------------------------------------------------
CHANGE IN UNREALIZED APPRECIATION (DEPRECIATION)                       (609,014)
--------------------------------------------------------------------------------
NET DECREASE IN NET ASSETS RESULTING FROM OPERATIONS                  $(107,695)
================================================================================

<PAGE>
16

STATEMENT OF CHANGES IN NET ASSETS
This Statement shows how the fund's total net assets changed during the two most
recent reporting periods. The Operations section summarizes information detailed
in  the  Statement  of  Operations.   The  amounts  shown  as  Distributions  to
shareholders  from the fund's net  income  and  capital  gains may not match the
amounts shown in the Operations section, because distributions are determined on
a tax  basis  and may be made in a period  different  from the one in which  the
income was earned or the gains were  realized on the financial  statements.  The
Capital Share Transactions section shows the amount shareholders invested in the
fund,  either by purchasing shares or by reinvesting  distributions,  as well as
the amounts redeemed.  The  corresponding  numbers of Shares Issued and Redeemed
are shown at the end of the Statement.

<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------
                                                                           INSTITUTIONAL INDEX FUND
                                                                    ---------------------------------
                                                                      SIX MONTHS                YEAR
                                                                           ENDED               ENDED
                                                                   JUN. 30, 2000       DEC. 31, 1999
                                                                           (000)               (000)
-----------------------------------------------------------------------------------------------------
<S>                                                                  <C>                 <C>

INCREASE (DECREASE) IN NET ASSETS
OPERATIONS
    Net Investment Income                                            $   198,034         $   398,042
    Realized Net Gain                                                    303,285           2,524,562
    Change in Unrealized Appreciation (Depreciation)                    (609,014)          3,298,626
                                                                      -------------------------------
      Net Increase (Decrease in Net Assets Resulting from Operations    (107,695)          6,221,230
                                                                      -------------------------------
DISTRIBUTIONS
    Net Investment Income
      Institutional Shares                                              (152,822)           (321,409)
      Plus Shares                                                        (36,427)            (79,609)
    Realized Capital Gain
      Institutional Shares                                                    --            (203,084)
      Plus Shares                                                             --             (49,082)
                                                                      -------------------------------
        Total Distributions                                             (189,249)           (653,184)
                                                                      -------------------------------
CAPITAL SHARE TRANSACTIONS-INSTITUTIONAL SHARES1
    Issued                                                             5,323,619          10,303,020
    Issued in Lieu of Cash Distributions                                 135,560             477,316
    Redeemed                                                          (4,503,124)         (8,693,972)
                                                                      -------------------------------
      Net Increase--Institutional Shares                                 956,055           2,086,364
                                                                      -------------------------------
CAPITAL SHARE TRANSACTIONS-PLUS SHARES2
    Issue                                                                998,736           3,550,850
    Issued in Lieu of Cash Distributions                                  32,394             119,924
    Redeemed                                                            (477,953)         (2,835,223)
                                                                      -------------------------------
      Net Increase--Plus Shares                                          553,177             835,551
-----------------------------------------------------------------------------------------------------
    Total Increase                                                     1,212,288           8,489,961
-----------------------------------------------------------------------------------------------------
NET ASSETS
    Beginning of Period                                               35,778,601          27,288,640
    End of Period                                                    $36,990,889         $35,778,601
=====================================================================================================

1Shares Issued (Redeemed)--Institutional Shares
    Issued                                                                40,598              85,337
    Issued in Lieu of Cash Distributions                                   1,002               3,891
    Redeemed                                                             (34,245)            (71,396)
                                                                      -------------------------------
       Net Increase in Shares Outstanding                                  7,355              17,832
=====================================================================================================

2Shares Issued (Redeemed)--Plus Shares
    Issued                                                                 7,544              29,551
    Issued in Lieu of Cash Distributions                                     240                 978
    Redeemed                                                              (3,679)            (23,207)
                                                                      -------------------------------
       Net Increase in Shares Outstanding                                  4,105               7,322
=====================================================================================================
</TABLE>

<PAGE>
17

FINANCIAL HIGHLIGHTS
This table  summarizes  the  fund's  investment  results  and  distributions  to
shareholders on a per-share basis for each class of shares. It also presents the
Total  Return and shows net  investment  income and expenses as  percentages  of
average net  assets.  These data will help you assess:  the  variability  of the
fund's  net  income  and  total   returns  from  year  to  year;   the  relative
contributions  of net income and capital gains to the fund's total  return;  how
much it costs to  operate  the fund;  and the  extent to which the fund tends to
distribute  capital gains.  The table also shows the Portfolio  Turnover Rate, a
measure of trading  activity.  A  turnover  rate of 100% means that the  average
security is held in the fund for one year.

<TABLE>
<CAPTION>
<S>                                               <C>       <C>         <C>        <C>        <C>         <C>
------------------------------------------------------------------------------------------------------------------
                                                              INSTITUTIONAL INDEX FUND INSTITUTIONAL SHARES
                                                                              YEAR ENDED DECEMBER 31,
FOR A SHARE OUTSTANDING                   SIX MONTHS ENDED    ----------------------------------------------------
THROUGHOUT EACH PERIOD                       JUNE 30, 2000       1999       1998       1997        1996      1995
------------------------------------------------------------------------------------------------------------------
NET ASSET VALUE, BEGINNING OF PERIOD               $134.02    $112.85     $89.56     $68.86      $57.93    $43.22
------------------------------------------------------------------------------------------------------------------
INVESTMENT OPERATIONS
    Net Investment Income                              .71      1.501      1.429      1.391        1.38      1.28
    Net Realized and Unrealized Gain (Loss)
      on Investments                                 (1.20)    22.143     24.177     21.415       11.90     14.86
                                                  ----------------------------------------------------------------
      Total from Investment Operations                (.49)    23.644     25.606     22.806       13.28     16.14
                                                  ----------------------------------------------------------------
DISTRIBUTIONS
    Dividends from Net Investment Income              (.68)    (1.514)    (1.416)    (1.391)      (1.36)    (1.27)
    Distributions from Realized Capital Gains           --      (.960)     (.900)     (.715)       (.99)     (.16)
                                                  ----------------------------------------------------------------
      Total Distributions                             (.68)    (2.474)    (2.316)    (2.106)      (2.35)    (1.43)
------------------------------------------------------------------------------------------------------------------
NET ASSET VALUE, END OF PERIOD                     $132.85    $134.02    $112.85     $89.56      $68.86    $57.93
==================================================================================================================

TOTAL RETURN                                        -0.37%     21.17%     28.79%     33.36%      23.06%    37.60%
==================================================================================================================

RATIOS/SUPPLEMENTAL DATA
    Net Assets, End of Period (Millions)           $29,644    $28,918    $22,338    $15,348     $11,426    $6,674
    Ratio of Total Expenses to
      Average Net Assets                            0.06%*      0.06%      0.06%      0.06%       0.06%     0.06%
    Ratio of Net Investment Income to
      Average Net Assets                            1.10%*      1.25%      1.46%      1.77%       2.18%     2.49%
    Portfolio Turnover Rate**                         11%*        14%        11%         7%          9%        4%
==================================================================================================================
 *Annualized.
**Portfolio  turnover rates excluding  in-kind  redemptions were 7%, 3%, 7%, 6%,9%, and 4%, respectively.
</TABLE>

<PAGE>
18

<TABLE>
<CAPTION>
<S>                                                         <C>        <C>         <C>                  <C>
FINANCIAL HIGHLIGHTS (CONTINUED)
------------------------------------------------------------------------------------------------------------------
                                                                        INSTITUTIONAL INDEX FUND PLUS SHARES
                                                                              YEAR ENDED DEC. 31,
                                                     SIX MONTHS ENDED    ------------------------      JUL. 7* TO
FOR A SHARE OUTSTANDING THROUGHOUT EACH PERIOD          JUN. 30, 2000       1999        1998        DEC. 31, 1997
------------------------------------------------------------------------------------------------------------------
NET ASSET VALUE, BEGINNING OF PERIOD                          $134.02    $112.85      $89.56               $84.91
------------------------------------------------------------------------------------------------------------------
INVESTMENT OPERATIONS
    Net Investment Income                                        .734      1.542       1.464                 .681
    Net Realized and Unrealized Gain (Loss)
      on Investments                                           (1.192)    22.143      24.177                5.455
                                                        ----------------------------------------------------------
      Total from Investment Operations                          (.458)    23.685      25.641                6.136
                                                        ----------------------------------------------------------
DISTRIBUTIONS
    Dividends from Net Investment Income                        (.702)    (1.555)     (1.451)               (.866)
    Distributions from Realized Capital Gains                      --      (.960)      (.900)               (.620)
                                                        ----------------------------------------------------------
      Total Distributions                                       (.702)    (2.515)     (2.351)              (1.486)
------------------------------------------------------------------------------------------------------------------
NET ASSET VALUE, END OF PERIOD                                $132.86    $134.02     $112.85               $89.56
==================================================================================================================

TOTAL RETURN                                                   -0.35%     21.21%      28.83%                7.29%
==================================================================================================================

RATIOS/SUPPLEMENTAL DATA
    Net Assets, End of Period (Millions)                       $7,347     $6,861      $4,951               $3,488
    Ratio of Total Expenses to Average Net Assets            0.025%**     0.025%      0.025%             0.025%**
    Ratio of Net Investment Income to Average Net Assets      1.14%**      1.29%       1.49%              1.72%**
    Portfolio Turnover Rate+                                    11%**        14%         11%                   7%
==================================================================================================================
 *Inception.
**Annualized.
 +Portfolio turnover rates excluding in-kind redemptions were 7%, 3%, 7%, and 6%, respectively.
</TABLE>

<PAGE>
19

NOTES TO FINANCIAL STATEMENTS
Vanguard Institutional Index Fund is registered under the Investment Company Act
of 1940 as a diversified  open-end  investment company, or mutual fund. The fund
offers two classes of shares,  Institutional Shares and Plus Shares. Plus Shares
are  designed   primarily  for   institutional   investors   that  meet  certain
administrative  and  servicing  criteria and have a minimum  investment  of $200
million.  Institutional Shares are offered to other institutional investors that
have a minimum investment of $10 million.

A. The following  significant  accounting policies conform to generally accepted
accounting  principles  for mutual  funds.  The fund  consistently  follows such
policies in preparing its financial statements.
     1. SECURITY  VALUATION:  Equity  securities are valued at the latest quoted
sales  prices  as of the  close  of  trading  on the  New  York  Stock  Exchange
(generally  4:00 p.m.  Eastern time) on the valuation  date; such securities not
traded on the valuation date are valued at the mean of the latest quoted bid and
asked  prices.  Prices are taken from the primary  market in which each security
trades.  Temporary cash investments acquired over 60 days to maturity are valued
using the latest bid prices or using  valuations based on a matrix system (which
considers such factors as security  prices,  yields,  maturities,  and ratings),
both  as  furnished  by  independent  pricing  services.  Other  temporary  cash
investments  are valued at amortized  cost,  which  approximates  market  value.
Securities for which market  quotations are not readily  available are valued by
methods deemed by the board of trustees to represent fair value.
     2.  FEDERAL  INCOME  TAXES:  The fund  intends to  continue to qualify as a
regulated   investment  company  and  distribute  all  of  its  taxable  income.
Accordingly,  no provision for federal income taxes is required in the financial
statements.
     3.  REPURCHASE  AGREEMENTS:  The fund,  along  with  other  members  of The
Vanguard Group,  transfers  uninvested cash balances into a pooled cash account,
which  is  invested  in  repurchase   agreements  secured  by  U.S.   government
securities.  Securities pledged as collateral for repurchase agreements are held
by a custodian bank until the agreements  mature.  Each agreement  requires that
the market value of the  collateral be sufficient to cover  payments of interest
and principal; however, in the event of default or bankruptcy by the other party
to  the  agreement,  retention  of  the  collateral  may  be  subject  to  legal
proceedings.
     4. FUTURES  CONTRACTS:  The fund uses S&P 500 Index futures  contracts to a
limited  extent,  with the objectives of maintaining  full exposure to the stock
market,  enhancing returns,  maintaining  liquidity,  and minimizing transaction
costs.  The fund may purchase futures  contracts to immediately  invest incoming
cash in the  market,  or sell  futures in  response  to cash  outflows,  thereby
simulating a fully invested position in the underlying index while maintaining a
cash  balance  for  liquidity.  The fund may seek to  enhance  returns  by using
futures contracts instead of the underlying securities when futures are believed
to be priced more attractively than the underlying securities. The primary risks
associated with the use of futures contracts are imperfect  correlation  between
changes  in market  values of stocks  held by the fund and the prices of futures
contracts, and the possibility of an illiquid market.
     Futures contracts are valued at their quoted daily settlement  prices.  The
aggregate  principal  amounts of the contracts are not recorded in the financial
statements.  Fluctuations  in the value of the  contracts  are  recorded  in the
Statement  of Net  Assets  as an  asset  (liability)  and in  the  Statement  of
Operations as  unrealized  appreciation  (depreciation)  until the contracts are
closed, when they are recorded as realized futures gains (losses).
     5.  DISTRIBUTIONS:  Distributions  to  shareholders  are  recorded  on  the
ex-dividend  date.  Distributions  are  determined on a tax basis and may differ
from net investment  income and realized  capital gains for financial  reporting
purposes.
     6. OTHER:  Dividend  income is recorded on the ex-dividend  date.  Security
transactions  are accounted for on the date securities are bought or sold. Costs
used to determine  realized gains (losses) on the sale of investment  securities
are those of the specific securities sold. Income,

<PAGE>
20

NOTES TO FINANCIAL STATEMENTS  (CONTINUED)

expenses not attributable to a specific class, and realized and unrealized gains
and losses on  investments  are  allocated  to each class of shares based on its
relative net assets.

B. The  Vanguard  Group  provides  investment  advisory,  corporate  management,
administrative,  marketing,  and  distribution  services  and pays for all other
operating  expenses,  except for taxes,  in return  for a fee  calculated  at an
annual percentage rate of the average net assets of the fund. For the six months
ended  June 30,  2000,  the  annualized  fees for such  services  were 0.06% and
0.025%,  respectively,  of average  net assets  for the  Institutional  and Plus
Shares  of the  fund,  of which  0.04%  and  0.005%,  respectively,  related  to
class-specific  shareholder services.  The fund's trustees and officers are also
directors and officers of Vanguard.

C. During the six months ended June 30, 2000, the fund purchased  $3,450,265,000
of investment securities and sold $1,988,077,000 of investment securities, other
than temporary cash investments.
     During the six months ended June 30, 2000,  the fund realized  $551,662,000
of net capital gains resulting from in-kind  redemptions-in  which  shareholders
exchanged  fund  shares for  securities  held by the fund  rather than for cash.
Because  such gains are not  taxable  to the fund,  and are not  distributed  to
shareholders, they have been reclassified from accumulated net realized gains to
paid in capital.

D. At June 30, 2000, net unrealized  appreciation  of investment  securities for
financial  reporting  and  federal  income  tax  purposes  was  $14,093,936,000,
consisting of unrealized gains of  $15,662,703,000  on securities that had risen
in value  since  their  purchase  and  $1,568,767,000  in  unrealized  losses on
securities that had fallen in value since their purchase.
     At June 30, 2000, the aggregate  settlement value of open futures contracts
expiring in September 2000 and the related unrealized depreciation were:

--------------------------------------------------------------------------------
                                                               (000)
                                                  ------------------------------
                                   NUMBER OF       AGGREGATE
                                     LONG         SETTLEMENT        UNREALIZED
FUTURES CONTRACTS                 CONTRACTS         VALUE          DEPRECIATION
--------------------------------------------------------------------------------
S&P 500 Index                        603          $221,316           $(4,919)
--------------------------------------------------------------------------------

E. The market value of  securities on loan to  broker/dealers  at June 30, 2000,
was  $7,597,000,  for which the fund held cash  collateral of  $9,469,000.  Cash
collateral received is invested in repurchase agreements.


<PAGE>

THE PEOPLE WHO GOVERN YOUR FUND

The  trustees of your mutual fund are there to see that the fund is operated and
managed in your best interests  since,  as a shareholder,  you are part owner of
the fund.  Your  fund  trustees  also  serve on the  board of  directors  of The
Vanguard  Group,  which is owned by the  funds  and  exists  solely  to  provide
services to them on an at-cost basis.
     Six of Vanguard's  seven board members are  independent,  meaning that they
have no  affiliation  with  Vanguard or the funds they  oversee,  apart from the
sizable personal investments they have made as private  individuals.  They bring
distinguished  backgrounds  in business,  academia,  and public service to their
task of working with Vanguard officers to establish the policies and oversee the
activities of the funds.
     Among board members' responsibilities are selecting investment advisers for
the  funds;  monitoring  fund  operations,  performance,  and  costs;  reviewing
contracts;  nominating  and  selecting  new  trustees/directors;   and  electing
Vanguard officers.
     The list below provides a brief description of each trustee's  professional
affiliations.  Noted in  parentheses is the year in which the trustee joined the
Vanguard board.

TRUSTEES

JOHN J. BRENNAN, (1987)  Chairman of the Board,  Chief  Executive  Officer,  and
Director/Trustee  of The  Vanguard  Group,  Inc.,  and  each  of the  investment
companies in The Vanguard Group.

JOANN HEFFERNAN HEISEN, (1998) Vice President, Chief Information  Officer, and a
member of the  Executive  Committee of Johnson & Johnson;  Director of Johnson &
Johnson*Merck Consumer Pharmaceuticals Co., The Medical Center at Princeton, and
Women's Research and Education Institute.

BRUCE K.  MACLAURY, (1990)  President  Emeritus  of The  Brookings  Institution;
Director of  American  Express  Bank Ltd.,  The St. Paul  Companies,  Inc.,  and
National Steel Corp.

BURTON G. MALKIEL, (1977)  Chemical  Bank  Chairman's  Professor  of  Economics,
Princeton  University;  Director of Prudential  Insurance Co. of America,  Banco
Bilbao Gestinova,  Baker Fentress & Co., The Jeffrey Co., and Select Sector SPDR
Trust.

ALFRED M. RANKIN, JR., (1993) Chairman, President,  Chief Executive Officer, and
Director of NACCO Industries, Inc.; Director of The BFGoodrich Co.

JAMES O. WELCH,  JR., (1971) Retired Chairman of Nabisco Brands,  Inc.;  retired
Vice Chairman and Director of RJR Nabisco;  Director of TECO Energy,  Inc.,  and
Kmart Corp.

J. LAWRENCE  WILSON,  (1985)  Retired  Chairman of Rohm & Haas Co.;  Director of
AmeriSource Health Corporation,  Cummins Engine Co., and The Mead Corp.; Trustee
of Vanderbilt University.

OTHER FUND OFFICERS
RAYMOND J.  KLAPINSKY
Secretary;  Managing  Director  and  Secretary  of  The  Vanguard  Group,  Inc.;
Secretary of each of the investment companies in The Vanguard Group.

THOMAS J. HIGGINS
Treasurer;  Principal  of The  Vanguard  Group,  Inc.;  Treasurer of each of the
investment companies in The Vanguard Group.

VANGUARD MANAGING DIRECTORS
R. Gregory Barton, Legal Department.
Robert A. DiStefano, Information Technology.
James H. Gately, Individual Investor Group.
Kathleen C. Gubanich, Human Resources.
Ian A. MacKinnon, Fixed Income Group.
F. William McNabb, III, Institutional Investor Group.
Michael S. Miller, Planning and Development.
Ralph K. Packard, Chief Financial Officer.
George U. Sauter, Quantitative Equity Group.

<PAGE>

ABOUT OUR COVER
Our cover art,  depicting HMS Vanguard at sea, is a reproduction  of Leading the
Way, a 1984 work created and  copyrighted by noted naval artist Tom Freeman,  of
Forest Hill, Maryland.

[SHIP LOGO]
[THE VANGUARD GROUP (R) LOGO]

Post Office Box 2600
Valley Forge, Pennsylvania 19482-2600

WORLD WIDE WEB
www.vanguard.com

FUND INFORMATION
1-800-662-7447

INDIVIDUAL ACCOUNT SERVICES
1-800-662-2739

INSTITUTIONAL INVESTOR SERVICES
1-800-523-1036

This report is intended for the fund's  shareholders.  It may not be distributed
to  prospective  investors  unless it is preceded or  accompanied by the current
fund prospectus.

Q942 082000
(C)2000 The Vanguard Group, Inc.
All rights reserved.
Vanguard Marketing
Corporation, Distributor.



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