The S&P 500 closed at a record high on October 6, 2026, above 7,800 for the first time, with only 24 of its stocks hitting yearly highs. Reporting since has established that roughly seven of the index's 500 companies drove the run, and that Nvidia, Apple and Microsoft are over 21 percent of the index, a record against the 1980s trio's 13.4 percent peak. Tech is now 37 percent of the index, above the dot-com peak of 34 percent, and the top five stocks equal the bottom 434. The discussion is about the widening split between AI and tech names and the rest of the market, with Goldman's breadth measure at its weakest since the dot-com bubble.