The S&P 500 has surged 142% since May 2024, but strip out AI stocks and that gain collapses to just 16%. The gap reveals a market dangerously reliant on a single theme.
AI stocks now account for 45% of the index's total market capitalization-an all-time high for any thematic cluster. The "Magnificent 7"-Apple, Microsoft, Nvidia-have pulled the entire index upward, masking underwhelming performance from the other 493 companies.
Capital Economics forecasts the S&P 500 hitting 7,250 by end of 2026, banking on continued AI momentum. Tom Lee of Fundstrat highlights "scarce assets" like Nvidia, AMD, Intel, and Micron, plus energy infrastructure plays GE Vernova and Caterpillar.
Behind the rally lies $1.4 trillion in AI-linked borrowing-corporate bonds, leveraged positions. The question isn't whether AI is real, but whether current prices already reflect years of future revenue growth. If projections slip, leverage could unwind quickly.
For investors holding plain S&P 500 index funds, nearly half of the portfolio is tied to one theme. The 16% ex-AI figure exposes a hidden concentration risk.