The S&P 500 market breadth has reached one of its weakest levels in at least 20 years, with only 5% of stocks hitting new 52-week highs, down sharply from 24% in November 2024. This narrow rally is driven by a handful of large-cap technology stocks, notably the "Magnificent 7," which now account for approximately 40% of the S&P 500's market capitalization and 26% of its earnings. NVIDIA's market capitalization alone represents a record 3.6% of global GDP and 13.4% of U.S. GDP, surpassing the market values of major economies like the UK, France, and Germany individually. The U.S. stock market capitalization to GDP ratio has hit a record 207%, exceeding the February 2025 high and well above the 2000 Dot-Com bubble peak of 140%. Valuations are elevated, with the S&P 500's next 12-month price-to-earnings ratio at 22, above the 20-year median of 16, and the Nasdaq 100 at 28. Retail investors have been heavily active, purchasing approximately $15 billion in stocks over five trading days and $155.3 billion in single stocks and ETFs during the first half of 2025, marking the largest six-month inflow on record. Their top holdings include NVIDIA ($472 billion), Apple ($284 billion), and Tesla ($256 billion), collectively exceeding $1 trillion. The U.S. market now represents about 70% of all developed market capitalization, a near-record divergence from European markets, which stand at 18%, the lowest since the 1980s. Despite some signs of improving breadth, the market's concentration and elevated valuations suggest fragility if the leading stocks falter.