Those who owned mutual funds that outperformed the competition in 2015, likely didn’t repeat their success in 2017, and an overwhelming majority of funds were unlikely to remain top performers over three- and five-year periods, a new study shows.

Further cementing the warning, “Past performance is not an indicator of future outcomes” that mutual funds are compelled to provide, new research from S&P Dow Jones shows outperforming other mutual funds year after year is increasingly rare. Researchers Aye M. Soe and Ryan Poirier checked the returns of some of 2015’s top performing mutual funds and found that the overwhelming majority failed to beat competing funds in 2017.

Of 563 domestic equity funds that were in the top performance quartile in September 2015, 6.3% managed to remain in the top quartile as of September 2017. That means, 93.6% of mutual funds did not. These numbers are largely the same among large-cap and small-cap funds, though mid-cap funds show an even more unimpressive 1.2% repeat top-quartile performance rate.

These results are even worse than last year’s study when 92.7% of funds failed to remain in the upper fourth of performers.

And the numbers don’t improve over time.

“An inverse relationship generally exists between the measurement time horizon and the ability of top-performing funds to maintain their status,” the authors wrote in a release that accompanied the study. “It is worth noting that no large-cap, mid-cap, or small-cap funds managed to remain in the top quartile at the end of the five-year measurement period.”

Even when it comes to remaining in the top half in their peer group, most mutual funds failed to do so. The survey’s authors note, over the three-year period ended September 2017, “persistence figures for funds in the top half were closer to the random expectation than that of the top quartile. Over three consecutive 12-month periods, 19.49% of large-cap funds, 18.52% of mid-cap funds, and 23.11% of small-cap funds maintained a top-half ranking.”

Furthermore, no mid-cap or small-cap funds were able to maintain their positions in the top quartile for even four years, the study found.

Despite pronouncements from Goldman Sachs’ chief equity strategist David Kostin, and others that 2017 would be a stock pickers’ market, “creat[ing] ‘winners’ and ‘losers’,” mutual fund managers’ stock picking has proven inconsistent. Kostin asserted that the election of Donald Trump push volatility and drive stock divergence.

Investors appear to have caught on to the trend, further pulling their cash out of mutual funds and putting it into “passive” investment vehicles like ETFs.

Bond mutual funds fared slightly better, providing “a few exceptions” to the rule over a five-year time horizon. The study found that funds investing in long-term government bonds, short-term investment-grade bonds and high yield bonds were “the only groups in which a noticeable level of persistence was observed.”

Dion Rabouin is a markets reporter for Yahoo Finance. Follow him on Twitter at @DionRabouin.

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