The U.S. stock market is exhibiting historically elevated valuations and concentration levels not seen since the Great Depression and the 2000 Dot-Com Bubble. Key valuation metrics including trailing P/E, forward P/E, Shiller P/E (CAPE), price-to-book, price-to-sales, EV/EBITDA, Q Ratio, and market cap to GDP ratio have all reached record highs. The Technology, Media, and Telecom (TMT) sector trades at nearly 27 times forward earnings, marking the highest level since the Dot-Com Bubble burst, with growth stocks also near 20-year valuation peaks. The top 10% of the largest U.S. stocks now account for approximately 76% of the total U.S. equity market capitalization, surpassing previous records set before the Great Depression and exceeding the 73% peak during the 2000 Dot-Com Bubble. Within the S&P 500, the top 10 stocks represent 40% of the market cap and 33% of profits. The dominance of the so-called "Magnificent Seven" tech giants skews sector weightings, with technology's share dropping from 34.5% to 19.4% when excluding these companies, allowing financials to become the largest sector at 21.1%. The U.S. constitutes 65% of the MSCI World Index, with tech and growth sectors trading at forward P/Es of approximately 27 and 26, respectively. Meanwhile, U.S. money market fund assets have grown to a record $7.9 trillion but represent only about 13.4% of the S&P 500's market cap, below the historical average of 19%, indicating limited potential inflows into equities. Additionally, retail investors' participation in the options market has surged to over 20% for the first time ever, surpassing the peak seen during the 2021 meme stock frenzy by roughly five percentage points.