U.S. stock market concentration now exceeds dot-com bubble levels, Yahoo Finance’s Brian Sozzi says. Earlier estimates showed the top 10 stocks could drive near

U.S. stock market concentration now exceeds dot-com bubble levels, Yahoo Finance’s Brian Sozzi says. Earlier estimates showed the top 10 stocks could drive nearly 75% of S&P 500 earnings growth in Q2, sharpening concern over narrow market leadership.