You might not think it’s possible to outperform the average Wall Street professional with just a single investment. Fund managers are highly educated and steeped in market data. They get paid a lot of money to make smart investments.

But the truth is, most of them may not be worth the money. With the right steps, individual investors can outperform the majority of active large-cap mutual fund managers over the long run. You don’t need a doctorate or MBA, and you certainly don’t need to follow the everyday goings-on in the stock market. You just need to buy a single investment and hold it forever.

That’s because 88% of active large-cap fund managers have underperformed the S&P 500 index over the last 15 years thru Dec. 31, 2023, according to S&P Global’s most recent SPIVA (S&P Indices Versus Active) scorecard. So if you buy a simple S&P 500 index fund like the Vanguard S&P 500 ETF (VOO -0.23%), chances are that your investment will outperform the average active mutual fund in the long run.

Why is it so hard for fund managers to outperform the S&P 500?

It’s a good bet that the average fund manager is hardworking and well-trained. But there are at least two big factors working against active fund managers.

The first is that institutional investors make up roughly 80% of all trading in the U.S. stock market — far higher than it was years ago when retail investors dominated the market. That means a professional investor is mostly trading shares with another manager who is also very knowledgeable, making it much harder to gain an edge and outperform the benchmark index.

The more basic problem, though, is that fund managers don’t just need to outperform their benchmark index. They need to beat the index by a wide enough margin to justify the fees they charge. And that reduces the odds that any given large-cap fund manager will be able to outperform an S&P 500 index fund by a significant amount.

The SPIVA scorecard found that just 40% of large-cap fund managers outperformed the S&P 500 in 2023 once you factor in fees. So if the odds of outperforming fall to 40-60 for a single year, you can see how the odds of beating the index consistently over the long run could go way down.

What Warren Buffett recommends over any other single investment

Warren Buffett is one of the smartest investors around, and he can’t think of a single better investment than an S&P 500 index fund. He recommends it even above his own company, Berkshire Hathaway.

In his 2016 letter to shareholders, Buffett shared a rough calculation that the search for superior investment advice had cost investors, in aggregate, $100 billion over the previous decade relative to investing in a simple index fund.

Even Berkshire Hathaway holds two small positions in S&P 500 index funds. You’ll find shares of the Vanguard S&P 500 ETF and the SPDR S&P 500 ETF Trust (NYSEMKT: SPY) in Berkshire’s quarterly disclosures. Both are great options for index investors, offering low expense ratios and low tracking errors (a measure of how closely an ETF price follows the underlying index). There are plenty of other solid index funds you could buy, but either of the above is an excellent option as a starting point.