Many Americans probably never think of their index funds as part of the healthcare debate, but Mark Cuban says they should.
Cuban argues that investors may already own some of the country's biggest health insurers without realizing it and is pushing fund managers to divest. The billionaire investor's warning highlights why it pays to understand what you actually own while trying to grow your wealth, especially since broad funds may include companies you might never choose individually.
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Cuban wants investors to pressure major health insurers
Cuban's criticism was aimed broadly at America's largest health insurers, which he accused of prioritizing shareholders over patients.
"If you own shares in a fund that owns any of the biggest insurance carriers, you are part of the cost of healthcare problem in this country," the billionaire wrote on X in August.
He went further, accusing those companies of putting "the share price over the health of you, your family, co-workers and friends" and urging investors to pressure the funds they own to divest. "Tell the funds you own that you will sell if they don't divest their interests in the biggest insurance companies," he wrote.
Cuban also argued that collective pressure could matter because millions of Americans participate in the stock market. The former Shark Tank star cited a figure of 61%, while Gallup's latest annual reading found that 62% of Americans owned stocks in 2025, including indirectly through mutual funds, 401(k)s, and IRAs.
Your index fund may already own insurance stocks
Investors don't need to intentionally buy an insurance stock to become shareholders, because broad-market index funds automatically own companies included in the indexes they track.
The iShares Core S&P 500 ETF (IVV), for example, held 504 securities as of late August, giving investors exposure to virtually every major industry represented in the S&P 500.
That exposure might be easy to miss because insurers may represent only a small fraction of a broad-market fund.
UnitedHealth is also a member of the Dow Jones Industrial Average. It accounted for about 4.4% of the SPDR Dow Jones Industrial Average ETF Trust (DIA) in late August, making the exposure particularly noticeable for investors tracking that index.
Healthcare funds may have much larger exposure
Broad-market funds might include insurers as relatively small positions, while sector-specific healthcare funds may devote a much larger share of their assets to them.
Fidelity's MSCI Health Care Index ETF held UnitedHealth at 5.48% of assets as of July 31, while CVS represented 1.92%, Elevance 1.19%, Cigna 1.09%, and Humana 0.63%. Together, those five companies represented roughly 10.3% of the fund.
A $10,000 investment would therefore have roughly $1,030 indirectly allocated to those five insurers, based on those weightings.
Some specialized funds are even more concentrated. Fidelity Select Health Care Services Portfolio held 25.28% in UnitedHealth, 14.99% in CVS, 9.09% in Elevance, and 3.51% in Humana as of July 31. Those four companies alone accounted for more than half of the portfolio.
Divesting isn't as simple as selling one stock
Someone who directly owns UnitedHealth shares could sell them without changing the rest of their portfolio. An index-fund investor usually can't.
An S&P 500 fund generally needs to maintain exposure to companies in its benchmark to track the index closely, so investors can't simply ask the manager to keep Apple and Microsoft while removing UnitedHealth or CVS. Following Cuban's suggestion could mean replacing the entire fund with one that intentionally excludes certain companies or industries.
Target-date retirement funds might create another layer of indirect exposure because they typically invest across a mix of broad stock and bond funds. This means a 401(k) investor may own insurers without seeing those company names anywhere on their account dashboard.
What Cuban's divestment push could mean for investors
A replacement fund may carry different fees, diversification, and performance, while investors in workplace retirement plans may have limited alternatives available. Building a portfolio of individual stocks offers more control but requires considerably more work.
Excluding major insurers would also cause returns to differ from the broad market because the portfolio would no longer own the same mix of companies as its benchmark. That difference could help or hurt performance depending on how those stocks perform.
Selling a fund also doesn't directly take operating cash away from an insurer. Most stock-market transactions transfer existing shares between investors, so the pressure Cuban is describing is more about shareholder demand, fund-manager behavior, and reputation.
Bottom line
Cuban's warning highlights something passive investors could easily overlook: Owning an index fund means owning the companies inside it, including businesses you might never choose individually.
If you are looking to start investing, you should not assume "passive" means hands-off forever. Understanding which companies sit inside a fund could help ensure the investment strategy and the businesses behind it still match your priorities.
This article is for informational purposes only and should not be considered investment advice.
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