Table of Contents
Table of Contents

How Vanguard Index Funds Work

Vanguard index funds use a passively managed index-sampling strategy to track a benchmark index. The type of benchmark depends on the asset type for the fund. Vanguard then charges expense ratios for the management of the index fund. Vanguard funds are known for having the lowest expense ratios in the industry. This allows investors to save money on fees and help their returns over the long run.

Vanguard is the largest issuer of mutual funds in the world and the second-largest issuer of exchange-traded funds (ETFs). John Bogle, Vanguard's founder, began the first index fund, which tracked the S&P 500 in 1975. Index funds with low fees are appropriate investments for the majority of investors. Index funds allow investors to gain exposure to the market in a single, simple, and easy-to-trade investment vehicle.

Key Takeaways

  • Vanguard is well-known for its pioneering work in creating and marketing index mutual funds and ETFs to investors.
  • Indexing is a passive investment strategy that seeks to replicate, rather than beat, the performance of some benchmark index such as the S&P 500 or Nasdaq 100.
  • To keep costs low, Vanguard often uses a sampling strategy to construct its index funds using less than the total number of assets in an index.
  • Vanguard offers funds that track a wide variety of market indices, large and small.

Passive Management

Passive management means the fund or ETF merely tracks the benchmark index. This is different from active management where a fund manager attempts to beat the performance of an index. For most active equity mutual funds, the benchmark index is the S&P 500.

Fees for active management are generally higher than for passively managed funds. Actively managed funds have higher trading costs since there is a greater turnover in fund holdings. These funds also have the additional costs of compensation for fund management. These factors lead to increased fees compared to passive funds.

Many actively managed funds fail to beat their benchmark indexes on a consistent basis. Higher fees combined with subpar performance leads to inferior results. Academic studies have shown higher fees alone lead to subpar performance for most active funds. Even if a fund manager is successful for a period of time, future success is not guaranteed. The risk of subpar performance is a major reason why passively managed index funds are a better option for most investors.

Index Sampling

Vanguard uses index sampling to track a benchmark index without necessarily having to replicate the holdings in the entire index. This allows the company to keep the fund expenses low. It is more expensive to hold every stock or bond in an index. Further, indexes do not have to allow for the inflow and outflow of funds like ETFs and mutual funds. Vanguard uses the index sampling technique to deal with the natural movement of capital for its funds while still replicating the performance of the benchmark index. Vanguard does not divulge its specific sampling technique.

Other common sampling techniques divide the index into cells that represent the different characteristics of the benchmark index. For a large stock index, the manager may divide the stocks in the index into different categories. These categories could include industry sector, market cap, price to earnings (P/E) ratio, country or region, volatility, or any number of other individual characteristics. The fund manager buys stocks or assets that mimic the performance of the components of the index.

The index sampling technique has the risk of a tracking error. A tracking error is the difference between the net asset value (NAV) of the fund’s holdings and the performance of the benchmark index over time. The greater the tracking error, the larger the discrepancy between the fund and the index. An index built using all stocks in the benchmark will have zero tracking error, but also be more costly to construct and maintain.

Expense Ratios

Vanguard funds charge expense ratios as their compensation for the management and issuance of the fund. The expense ratio is calculated by taking the fund’s operating costs and dividing them by the assets under management (AUM). Vanguard’s expense ratios are some of the lowest in the industry. The expense ratios for its mutual funds are generally 82% less than the industry average.

Expense ratios can have a significant impact on returns over time. Vanguard notes that for a hypothetical investment of $50,000 over 20 years, and investors could save around $24,000 in expenses, assuming a 6% annual rate of return. This is a substantial amount. Investors should, therefore, seek to invest in funds with low expenses.


Vanguard charges an expense ratio of as little as 0.03% per year on some of its index mutual fund products.

Example: Vanguard Total Stock Market Index Fund (VTSAX)

As an example, let us look more closely at one of Vanguard's broad stock market index mutual funds. The Vanguard Total Stock Market Index Fund (VTSAX) provides diversified exposure to small-, mid-, and large-cap growth and value stocks traded on the Nasdaq and New York Stock Exchange (NYSE).

Created on April 27, 1992, the mutual fund has achieved an average annual return of 8.87% since its inception (as of March 31, 2020). The fund's Admiral Shares—the only ones currently available to new investors—have returned an average of 5.79% annually since their inception on Nov. 13, 2000. This return is almost identical to that of the fund's benchmark, the CRSP U.S. Total Market Index. The fund employs a representative sampling approach to approximate the entire index and its key characteristics.

As of Q2 2022, the fund held 4,124 stocks and controlled total net assets of $1.3 trillion. Technology, financial, industrial, health care, and consumer service companies make up its largest holdings. VTSAX charges an extremely low expense ratio of just 0.04%, but requires a minimum investment of $3,000.

What Was Vanguard's First Mutual Fund?

Vanguard launched its first mutual fund in 1975, known as the First Investment Trust. It was intended to passively track the S&P 500 index, and in 1981 changed its name to the Vanguard 500 Fund. At the time, it was met with great skepticism, as mutual funds up until that point had been actively-managed investments.

How Large Are Index Funds?

Index funds that track broad stock market indices are now a dominant force on Wall Street. Today, the 13 largest stock funds around all track indexes. In 2010, index funds represented less than one-fifth of total equity fund market share. By 2020, this grew to more than 40%, In 2019, the total assets invested in U.S. stock index funds for the first time surpassed the assets of funds actively managed by human beings.

What Is the Largest Mutual Fund in the World?

The Vanguard Total Stock Market Index Fund (VTSAX) ranks first with an astounding $1.3 trillion in assets under management (AUM). Even with just a 0.04% expense ratio, the fund is able to generate $520 million in fee revenue each year.

How Can Vanguard Keep Its Fees So Low?

By specializing in passively-managed index funds, overhead and turnover are very low. Little money has to be spent on research and analysis, since the funds replicate existing indexes. Moreover, Vanguard commands large economies of scale, which lowers total costs for the company and savings can be passed on to its customers.

Article Sources
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  1. Vanguard. "VTSAX."

  2. Wall Street Journal. "Birth of the Index Mutual Fund: ‘Bogle’s Folly’ Turns 40."

  3. Kiplinger. "The Truth About Index Funds."

  4. Vanguard. "Low investment fees and costs mean you keep more for you."

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