This distribution is the second largest on record, trailing only the railroad mania of 1881, which hit 63% concentration. The move puts AI stocks above the weighting levels of every other major market bubble in modern history.
Tuesday, October 20, 2026
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AI Stocks Hit 49% of S&P 500 in 2nd Largest Concentration in History
US Markets1 day ago
A surge in valuations for software and chip designers has altered the composition of the primary US stock index. These AI-related assets now occupy 49% of the S&P 500, a figure that surpasses the 41% concentration seen during the peak of the dot-com bubble and the 44% allocation of the Japanese market in 1988.
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