Passive index funds now 51% of investors

The “51%” claim attached to passive investing is real in one narrow sense and unverified in the broader one circulating online. Investment Company Institute data show index mutual funds and exchange-traded funds reached 51% of all long-term U.S. mutual fund and ETF net assets at year-end 2024, according to an ICI research report published in March 2025. That supports a statement about assets in long-term funds and ETFs, not a statement that passive products now account for 51% of all investors. Morningstar and S&P Dow Jones Indices publish separate work on active-versus-passive performance, but those reports do not describe passive investing as 51% of investors. ### Where does the 51% number actually come from? ICI said in its March 2025 report on fund fees and expenses that the share of assets in index mutual funds and ETFs rose from 19% at year-end 2010 to 51% at year-end 2024. The report described the measure as “all long-term mutual fund and ETF net assets,” which excludes money market funds and is framed around assets under management, not headcount. (ici.org) Pensions & Investments reported on March 26, 2025 that index mutual funds and ETFs had “capturing 51% of assets under management in 2024,” attributing the figure to ICI. A separate industry summary citing ICI data said passive mutual funds and ETFs reached $15.96 trillion in March 2025, or 51% of total mutual fund industry assets at that point. (ici.org) ### Does that mean passive funds are 51% of investors? ICI’s shareholder data point in a different direction because they measure households and mutual fund ownership, not the asset split between active and index products. ICI said 53.9% of U.S. households owned mutual funds in 2025, representing 123.2 million individual mutual fund shareholders, but that figure does not separate passive from active ownership. (pionline.com) Morningstar’s U.S. Active/Passive Barometer also does not support the “51% of investors” wording. Its year-end 2025 report covered about $26 trillion in assets, or roughly 67% of the U.S. fund market, and compared the results of active funds against passive peers. That is a performance study, not a census of how many investors use passive products. (iciglobal.org) ### Why are people tying the number to the S&P 500? Vanguard’s filings show that major index products are built to track benchmarks such as the S&P 500 and hold the same stocks in benchmark weights. The Vanguard 500 Index Fund prospectus says the fund uses an indexing approach to track the S&P 500, and Vanguard’s S&P 500 ETF describes the index as covering large U.S. companies. (morningstar.com) S&P Dow Jones Indices’ SPIVA reports provide one reason passive products have kept attracting money: most active large-cap U.S. equity funds have lagged the S&P 500 over long periods, and 79% underperformed in 2025, according to the year-end scorecard. Morningstar said only 21% of active funds survived and beat their average indexed peer over the decade through 2025. Those reports address performance and fund selection, not whether passive ownership shields specific companies from market pressure. (personal1.vanguard.com) ### Can the 51% figure prove that big companies are protected? SEC Form 13F data and fund filings can show that large managers and index funds hold substantial stakes in public companies, but the social-media version of the argument did not point to a study demonstrating that 51% passive asset share causes insulation for S&P 500 companies. The SEC’s 13F data sets are a source for institutional holdings, while fund prospectuses describe index-tracking methods and diversification limits. (spglobal.com) Neither source, on its own, establishes the market-effect claim in the post. The cleaner way to state the story is narrower. ICI’s published data support that passive index mutual funds and ETFs crossed 51% of long-term U.S. fund and ETF assets by the end of 2024, and later monthly ICI releases showed indexed assets remained ahead of active assets into 2026. The next update is ICI’s monthly active-and-index release for April 2026, posted on the group’s statistics page. (ici.org) (sec.gov)