As of March 2025, the concentration of the largest U.S. stocks has reached a record 75% of the stock market, surpassing levels seen before the Great Depression and the Dot-Com Bubble. This extreme concentration raises concerns regarding market stability. Notably, U.S. households have also allocated the highest proportion of their assets to stocks in history, while cash allocations remain historically low. Prominent investors, including Warren Buffett, have been selling stocks and accumulating cash, with Buffett's cash reserves hitting a record $334 billion, representing 29% of his assets. Leon Cooperman has expressed bearish sentiments about the market, stating he is selling into strength and holding a cash position of 15%, citing high valuations and policy uncertainty. The overall dominance of U.S. stocks, which now account for nearly two-thirds of the global investable market, has sparked debate about potential risks for investors' portfolios.