The S&P 500 has surged 117% since October 2022, adding nearly $40 trillion in market value, largely driven by AI-related stocks. This rally, however, shows narrow leadership, with the equal-weight S&P 500 underperforming by a record 52 percentage points. Nvidia's stock is up over 1,900%, and Treasury yields recently hit 5.34%, raising investor focus on whether earnings growth can sustain the bull market.