50% of the S&P 500 Is One Bet. Nvidia Is Lending to Its Customers. Are You Buying What Already Won?

The S&P 500’s heavy concentration in AI-linked technology giants creates significant risks for passive investors, as these indices often prioritize price momentum over fundamental value. Rob Arnott, founder of Research Affiliates, argues that technological revolutions historically create bubbles where market leaders are priced for perfection, yet long-term value often accrues to the technology's adopters rather than the infrastructure builders. The "privileges of membership" in major indices force passive funds to buy stocks at inflated valuations, creating inefficiencies that active strategies can exploit. Furthermore, traditional accounting fails to capture the true value of intangible investments like R&D, which are often treated as expenses rather than capital assets. Investors should look beyond market-cap-weighted indices toward strategies that emphasize fundamental growth and avoid the pitfalls of performance chasing to achieve superior long-term returns.