At The Money: Looking Beyond Market Cap Weighted Indexes

In this episode of Bloomberg's At The Money, host Barry Ritholtz explores the growing concerns around market cap-weighted indexes like the S&P 500, which have become increasingly concentrated in a handful of mega-cap stocks—commonly known as the Magnificent Seven. The episode features Rob Barnott, founder of Research Affiliates and a long-time critic of cap-weighted indexing, who argues that these indexes are fundamentally flawed because they reward past performance and amplify market bubbles. Barnott presents a compelling case for fundamental indexing, which weights stocks based on economic metrics like sales, profits, dividends, and net worth rather than market price. He explains how this approach naturally downweights overvalued growth stocks and upweights undervalued, economically significant companies, creating a more resilient and value-oriented portfolio. The discussion also covers the hidden costs of index changes—such as the 'flip-flop' effect when stocks are added or removed—and how even equal-weighting strategies can suffer from biases if applied to cap-weighted indexes. With over $100 billion in assets now tied to fundamental indexing strategies, Barnott demonstrates that these approaches have consistently outperformed traditional value and growth indexes over two decades, delivering a 2-2.5% annual outperformance with lower volatility. The episode concludes with a strong endorsement for investors seeking to reduce concentration risk and improve long-term risk-adjusted returns by moving beyond passive cap-weighted models.