Every Bubble Peaked Near 40% - AI Is There Now

Ten AI companies now make up about 41% of the entire US stock market, according to BofA. The group is the Magnificent Seven plus Broadcom, AMD and Micron. That matches the peaks of the Nifty Fifty (40%) and the dot-com bubble (41%), and it’s close to Japan in 1989 (44%). Only the railroads of the 1880s ever went higher, at 63%.

BofA’s point isn’t just the size. The bank says these booms usually end when inflation drives bond yields up, and oil near $100 is feeding exactly that pressure. Meanwhile the rest of the market is already weakening: roughly 400 S&P 500 stocks trade below their 50-day averages. If the AI giants stumble, very little is left to hold the index up.

And concentration could still rise. BofA notes that if SpaceX, OpenAI and Anthropic go public and join the group, US concentration would pass every bubble on record except the railroads.

Data source 🔗 BofA Global Research

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