Investors who followed Warren Buffett's advice to buy and hold a low-cost S&P 500 index fund have seen their money quadruple over the past decade, but new data shows most active managers failed to keep up
Warren Buffett has long urged investors to skip stock picking and instead put their money in a low-cost S&P 500 index fund. Over the past ten years, that approach has delivered results that most professional managers failed to match. According to data cited by The Motley Fool, a $10,000 investment in the Vanguard S&P 500 ETF (VOO) made in mid-2016 would have grown to more than $40,000 by late July 2026, assuming dividends were reinvested. That's a total return of 303% over the decade, not including the effects of inflation or taxes.
The Vanguard S&P 500 ETF, which Buffett specifically referenced in his 2013 Berkshire Hathaway shareholder letter, tracks the S&P 500 by holding all 500 stocks in the index, weighted by market capitalization. Its annual expense ratio is just 0.03%, meaning investors pay $3 per year for every $10,000 invested-far below the 0.72% average for similar large-cap equity funds, according to Vanguard. As of June 2026, VOO became the first ETF to surpass $1 trillion in assets, reflecting a broader shift among investors toward passive index funds and away from higher-cost active management.
Active Managers Struggle to Keep Up
While index fund investors have enjoyed strong gains, most active fund managers have not kept pace. The S&P Indices Versus Active Funds (SPIVA) scorecard, which tracks how actively managed funds perform against their benchmarks, found that 79% of actively managed large-cap equity funds lagged the S&P 500 in 2025. That was up sharply from 65% the previous year and marked the fourth-worst result in the report's 25-year history. Over the 15 years ending December 2025, there was not a single equity fund category in which a majority of active managers beat their benchmark, according to the SPIVA data.
These results reinforce Buffett's argument that most investors are better off with a diversified, low-cost index fund than trying to pick individual winners or pay for active management. The cumulative effect of higher fees and the difficulty of consistently outperforming the market have made it challenging for active managers to deliver better long-term results for their clients.
Risks of Index Concentration
Despite the strong historical performance, some Wall Street strategists have raised concerns about the S&P 500's growing concentration in a handful of mega-cap technology stocks. By the end of 2025, the ten largest companies in the index accounted for 40.7% of its total weight, nearly double their share a decade earlier, according to RBC Wealth Management. This means that a sharp decline in just a few dominant stocks could drag down the entire index, even if the rest of the market holds up.
Some investment advisers now caution that a "set-it-and-forget-it" approach focused solely on the S&P 500 may not provide the same level of diversification as in the past, especially for investors with shorter time horizons or lower risk tolerance. The decision to rely on a single index fund should take into account factors such as savings rate, investment timeline, and comfort with market swings.
Index Fund Growth and Investor Behavior
The surge in assets flowing into index funds like VOO reflects a broader trend among U.S. investors. In the first half of 2026 alone, VOO attracted more than $69 billion in net inflows, according to InvestmentNews. Combined with its mutual fund share class, the underlying Vanguard 500 Index Fund now holds about $1.6 trillion in total assets. This shift has been driven by the appeal of low fees, broad diversification, and the difficulty most active managers face in beating the market after costs.
For many investors, the simplicity and transparency of index funds have become more attractive than the promise of outperformance from active management. Still, the growing dominance of a few stocks within the S&P 500 has prompted some experts to recommend reviewing portfolio allocations and considering additional diversification, especially as market conditions evolve.
According to Vanguard, the average expense ratio for all U.S. equity mutual funds and ETFs was 0.44% in 2025, compared to just 0.03% for VOO. Over time, even small differences in fees can have a significant impact on investment returns, especially when compounded over decades.
While the past decade has rewarded those who followed Buffett's advice, future results will depend on market conditions, the performance of the largest index constituents, and each investor's personal goals and risk tolerance. As always, past performance is not a guarantee of future results, and investors should review their strategies regularly to ensure they remain aligned with their objectives.
The S&P 500 index is a market-capitalization-weighted benchmark of 500 of the largest publicly traded companies in the United States. Because the largest companies have a greater influence on the index's performance, periods of rapid growth or decline in a few mega-cap stocks can have an outsized impact on returns. Investors considering index funds should understand how this concentration risk can affect their portfolios, especially if they rely heavily on a single fund for long-term growth. Diversification across asset classes, sectors, and geographies can help manage risk, but it may also reduce the potential for outsized gains during periods when a narrow group of stocks leads the market.
