By early 2025, the top 10 companies in the S&P 500 accounted for approximately 38% to 40% of the index's market capitalization, reaching levels not seen in 60 years and surpassing even the peak concentration during the 2000 dot-com bubble. Meanwhile, the next 40 stocks in the index represented only about 22.8% of the market cap, the lowest on record. Earnings reports for the first quarter showed that 78% of S&P 500 companies beat earnings per share estimates, slightly above the five-year average of 77%, and 63% beat revenue estimates, which is below the five-year average of 69%. Year-over-year earnings growth for the index was 12.9%, exceeding the March 31 estimate of 7.1%, while revenue growth was 4.9%, above the estimated 4.3%. Despite these positive earnings results, valuations remain elevated, with the S&P 500's forward 12-month price-to-earnings (P/E) ratio at 21.1, above both the five-year average of 19.9 and the ten-year average of 18.4. The trailing 12-month P/E ratio stands at 25.6, also exceeding historical averages. The Nasdaq 100's P/E ratio reached 26x, another historically high level. These valuation metrics, combined with a decade of strong annual returns averaging about 13% for the S&P 500—a period only surpassed by the 1990s—suggest that the era of above-average stock market gains may be coming to an end. Meanwhile, international and Eurozone stocks have seen substantial gains in 2025, rising 14% and 24% respectively, contrasting with a 1% decline in the S&P 500, indicating a potential shift in global market leadership after more than 16 years of US stock outperformance.