S&P 500 index funds increasingly resemble tech funds, warns analyst

The classic advice for retail investors has always been simple: buy an S&P 500 index fund, hold it forever, and let diversification do the heavy lifting. There’s just one problem. That “diversified” index fund now looks a lot like a tech sector bet. Broader technology sectors, including communications services and tech-adjacent firms, now account for more than 50% of the S&P 500’s roughly $70 trillion market capitalization. The Information Technology sector alone represents about one-third of the index, driven largely by semiconductor and AI-linked companies that have surged during the AI boom. A concentration problem that dwarfs the dot-com bubble The top 10 companies in the S&P 500 now comprise approximately 40% of the index’s total market value. For context, at the peak of the dot-com bubble in 2000, that figure was around 27%. The mechanics of market-cap-weighted indexing make this a self-reinforcing cycle. When a stock rises, it occupies a larger share of the index. Index funds then allocate more new money to that stock, pushing it higher still. The three largest S&P 500 ETFs, SPY, IVV, and VOO, collectively manage nearly $2.7 trillion in assets. Every dollar f...