When SpaceX joined the Nasdaq-100 index on 7 July 2026, following a rule change it had itself requested allowing large newly public firms to join after just 15 days of trading, index funds tracking the benchmark were forced to buy its shares. This raised questions about whether a single, highly valued and reportedly overpriced company entering a major index could threaten the stability of funds that millions of ordinary savers rely on for low-risk, long-term investing.

Index funds, popularised by economist Burton Malkiel's 1973 book "A Random Walk Down Wall Street" and endorsed by Warren Buffett, work by tracking a whole market rather than picking individual stocks, and passive investing overtook active fund management in assets under management in 2024. Malkiel, interviewed for the piece, said he would be wary of buying SpaceX shares individually given the roughly $1.77 trillion valuation, but argued its inclusion does not undermine the broader case for index investing. The piece notes that anticipation of forced index-fund buying may have contributed to unusual trading patterns around SpaceX's stock, including a dip just before its index inclusion, benefiting some banks and hedge funds.