Dot Com Bubble vs. AI Bubble: 2000 and 2026 Compared

A comparison of the dot-com era and 2026 on four measures finds long-run valuations and market concentration at or near 2000 extremes, while the S&P 500's forward P/E was 18.7 on October 30, 2026 versus 24.4 in March 2000, and the Nasdaq's 6.8% decline from its October 6, 2026 record is far short of the 77.9% dot-com crash. Tech stocks were 39.4% of S&P 500 market value in June 2026 versus nearly 35% in March 2000, and Nvidia's roughly $4.99 trillion market value dwarfs Cisco's $579 billion peak. St. Louis Fed researchers estimated AI-related investment added 0.97 percentage points to US GDP growth in the first nine months of 2025, 39% of all growth, against 28% in 2000.