Market concentration—the dominance of a few mega-cap stocks—is a persistent concern for investors, especially after recent AI-related volatility. However, a paper by Mark Kritzman of MIT Sloan and David Turkington of State Street Associates, titled *The Fallacy of Concentration*, argues that this anxiety is misplaced. Their analysis shows that while concentration in the S&P 500 is at its highest since 1998, trying to hedge against it by shifting to cash or underweighting equities has historically backfired. From 1936 to mid-2025, a simple buy-and-hold strategy in U.S. stocks generated over twice the wealth of a dynamic strategy that reduced stock exposure during high-concentration periods, with less risk. Similar results held across five other major markets from 1983 onward. The authors conclude that concentration is real but not actionable—investors are better off ignoring it and staying fully invested.
The article also briefly previews U.S. midterm election outcomes and their potential market impacts, including Iran, AI regulation, fiscal policy, and crypto oversight. But the core message remains: don’t let concentration fears drive portfolio decisions.
Source: Financial Times Companies · Summarized by HeadlinesBriefing