A $10,000 investment in an S&P 500 index fund a decade ago could now be worth over $38,000. But recent returns far outpace the long-term average, and most managed funds still lag behind this broad market benchmark.
For investors seeking broad exposure to the U.S. stock market, S&P 500 index funds have delivered a decade of notable growth-turning $10,000 into more than $38,000, or over $41,000 with dividends reinvested. However, these headline figures reflect an unusually strong period for stocks over the past 15 years, and future returns may differ significantly.
In 2023, U.S. index funds surpassed actively managed funds in total assets for the first time, marking a major shift in investor preference toward passive investing.
How S&P 500 Funds Stack Up
Recent performance has been striking. According to Morningstar, the S&P 500 delivered an average annual gain of 15.38% over the past 10 years and 15.45% over the past 15 years, as of September 3, 2026. The average for the past three years was even higher at 21.25%. These results are well above the index's long-term historical average, which is closer to 10% per year before inflation.
For perspective, the S&P 500 has outperformed approximately 90% of actively managed large-cap mutual funds over the last 15 years, based on S&P Dow Jones Indices data through the end of 2025. This consistent outperformance is a key reason why investors such as Warren Buffett have repeatedly recommended low-cost S&P 500 index funds-specifically highlighting the Vanguard S&P 500 ETF (VOO) for its cost efficiency and broad market exposure.
What's Inside the Index
The S&P 500 is more than a list of 500 companies. It is weighted by market capitalization, so the largest firms have the greatest influence on returns. As of July 31, 2026, the top holdings in the Vanguard S&P 500 ETF included Nvidia (7.55%), Apple (7.04%), Microsoft (5.36%), Amazon.com (4.13%), and both Alphabet share classes (3.24% and 2.62%). Other significant weights included Broadcom, Meta Platforms, JPMorgan Chase, and Berkshire Hathaway Class B.
The S&P 500 index is reviewed quarterly by a committee at S&P Dow Jones Indices, which can add or remove companies based on criteria such as market capitalization, liquidity, and sector representation. This process ensures the index remains a dynamic reflection of the U.S. large-cap market.
Risks and Practical Considerations
Despite its strong historical record, the S&P 500 does not guarantee future results. The last 15 years have been unusually favorable for U.S. equities, and there is no assurance that such high returns will continue. Investors should not expect 15% annual gains to persist indefinitely. Over the long term, the index's average annual return has been closer to 10%, and this figure does not account for inflation, taxes, or investment fees.
Index funds such as the Vanguard S&P 500 ETF typically offer low expense ratios, helping investors retain more of their returns. However, even modest fees can erode gains over decades. Investors should also consider their own time horizon, risk tolerance, and the need for diversification beyond large-cap U.S. stocks. While the S&P 500 covers a broad segment of the market, it does not include small-cap, international, or alternative assets.
For those comparing different types of index funds, it is important to note that other asset classes-such as gold-have distinct risk and return profiles. For example, as reported earlier, gold ETFs like SPDR Gold Shares can provide a hedge against inflation but involve different costs and market dynamics than stock-based funds.
Understanding Index Investing
Index funds are structured to track the performance of a specific market benchmark, such as the S&P 500, by holding all or a representative sample of the securities in that index. This passive approach contrasts with actively managed funds, where managers attempt to outperform the market through security selection and timing. Over time, the lower fees and broad diversification of index funds have made them a popular choice for retirement accounts and long-term investors.
One significant advantage of index investing is transparency: investors know exactly what they own and how the fund is constructed. However, index funds will never outperform the market they track and are fully exposed to market downturns. Investors should carefully consider these trade-offs when deciding how much of their portfolio to allocate to index funds versus other strategies or asset classes.
Market capitalization weighting, as used by the S&P 500, means that the largest companies have the greatest impact on returns. This can result in periods where a small group of stocks drives most of the gains or losses in the index. Equal-weighted funds, sector funds, and international funds offer alternative approaches for those seeking different risk exposures or diversification benefits.
