The U.S. stock market is experiencing unprecedented concentration, with the top 10 stocks accounting for 59% of the S&P 500's gains since the market bottomed in October 2022. This concentration is highlighted by the fact that the top three stocks—Apple, Microsoft, and Nvidia—now represent 21% of the S&P 500's total market cap. Additionally, the top 10 stocks reflect a record 40% of the index's market value, a figure that is double the percentage seen seven years ago and significantly higher than the 2000 Dot-Com Bubble peak. The market's current stock market to GDP ratio has reached 204%, surpassing the previous record of 200% set before the 2022 bear market. This level of concentration and valuation has raised concerns, as the last time such a concentration was observed was just before the Great Depression in 1929.