Market concentration in the S&P 500 has reached unprecedented levels, with the top 10 stocks now accounting for 37% of the index's market capitalization. This figure surpasses the previous record set during the Dot-Com Bubble by 10 percentage points. Notably, technology stocks alone represent 33% of the S&P 500's market cap, exceeding the Dot-Com Bubble by 2 percentage points. When including Communication Services, these sectors collectively account for 43% of the market, which is double the concentration observed in the Financials Bubble of 2007. Furthermore, the top 10 U.S. firms now hold 18% of the global stock market capitalization, the highest since the 1970s and above the 13% recorded during the 2000 Dot-Com Bubble. Additionally, nearly 50% of the S&P 500's market cap is currently under investigation by antitrust regulators.