The U.S. stock market is facing unprecedented levels of concentration and valuation, raising concerns about a potential bubble. The PEG ratio for the so-called 'Magnificent 7' stocks has reached 4.2x based on projected earnings for 2024-2026. Analysts note that the largest U.S. firm's market capitalization is approximately 750 times larger than that of the 75th percentile stock, surpassing previous market bubbles. The current ratio exceeds the peak seen during the 2000 Dot-Com Bubble, which was around 580x. Furthermore, the market capitalization of all active U.S. stocks has now surpassed twice the nation's GDP, marking a historic first. The U.S. accounts for 74% of the MSCI world market capitalization, a significant increase compared to Japan's 45% share during its bubble in the 1980s. The ratio of the market capitalization of U.S. non-financial firms to their gross value-added has also hit over 3x, exceeding the peaks of 1929, 2000, and 2022. Additionally, the forward price-to-earnings ratio for the top 10 S&P 500 stocks is around 30x, which is higher than the 25x ratio during the Dot-Com Boom. Notably, the S&P 500's market value now constitutes 46% of the global economy, a percentage that has doubled in recent years, compared to 38% at the peak of the Dot-Com bubble.