Stock Market Concentrates Wealth Among Few

Finance professor Hendrik Bessembinder's updated research, covering roughly 29,000 U.S. stocks from 1926 through 2025, finds extreme concentration of long-term shareholder wealth. The study reports that as few as two companies account for 10% of net market wealth, median lifetime stock returns are negative (-6.9%), and under 4% of firms generated essentially all net U.S. stock market wealth. The findings favor broad diversification.