Jeremy Grantham warns U.S. stocks are at record valuations

Veteran investor Jeremy Grantham said U.S. stocks have reached the most expensive level in American history, based on market value relative to GDP with some adjustments. He made the remarks in an interview with CNBC's Squawk Box on June 26, 2026. Grantham said the 2000 tech bubble is the closest historical comparison, and he pointed to the Buffett indicator as another measure suggesting elevated valuations. He noted that the ratio of U.S. market capitalization to GDP is estimated at about 235%, meaning the stock market is worth more than twice the size of the economy. He also said the artificial intelligence boom has contributed to investor enthusiasm, citing SpaceX's roughly $2 trillion valuation as another sign of stretched sentiment. While Grantham said the timing is uncertain, he argued that the market could eventually face a major decline and that some current conditions resemble a peak.