Analysis: AI leader stocks drive the S&P 500 up 117% in a bull market, intensifying market concentration risk.

October 9 — Market analysis indicates that since October 2022, the S&P 500 has gained 117%, driving a nearly $40 trillion increase in total U.S. stock market capitalization, with the rally primarily fueled by AI-related stocks.

Meanwhile, the S&P 500 equal-weight index has underperformed the market-cap-weighted index by 52 percentage points, marking the largest gap in history and highlighting this bull market's reliance on a handful of large-cap tech stocks.

Nvidia's stock price has surged over 1,900% during the same period, while U.S. Treasury yields recently climbed to 5.34%, further raising concerns about valuation pressures. Investors are closely watching whether corporate earnings growth can continue to sustain this bull market.