AI stocks lift S&P 500 while ex-AI index stalls

AI-linked companies, now roughly 45% of the S&P 500’s market capitalization, account for almost all of the benchmark’s gains in 2026 while the S&P 500 ex-AI measure has shown little movement since February.

The S&P 500 has reached fresh record highs this year. The index rose nearly 7% from early February, experienced losses in March amid volatility tied to the Israel‑Iran conflict, and then accelerated its rebound in April. From March 30 through early May the benchmark gained about 15.5%.

An index that removes AI enablers, the US 500 Excluding Artificial Intelligence Enablers Price Return Index (SPXXAI), has declined about 1.84% since its launch in February, according to index data. The divergence between the headline S&P and the ex‑AI measure highlights a concentration of returns in a relatively small group of large-cap AI names.

Over a three-year span through early 2026, the headline S&P posted a total return near 76%, while the ex‑AI version returned about 32%, based on analysis by Goldman Sachs. The larger market gains have been led by major cloud providers and other firms marketed as AI enablers.

The pattern is visible outside the U.S. as well. Asian equity markets have seen rallies driven by large technology and AI-related stocks that have offset broader economic pressure and investor uncertainty linked to the Middle East tensions. Fabien Yip, market analyst at IG International, noted: “Outside of AI, there is a genuine absence of catalysts, and many companies’ spending plans and margin outlooks remain on hold until there is greater clarity on the conflict.”

Measures of market breadth show uneven gains. While headline indices have reached records, many sectors and smaller-cap stocks have lagged. Earnings guidance and capital expenditure plans at firms not tied to AI remain cautious, and some companies are delaying spending decisions.

Investors and strategists are monitoring index composition and sector flows to assess whether gains broaden beyond AI-related firms. The size of the AI-related cohort-about half the S&P by market value-means continued outperformance by that group can lift the overall index even if most constituents show limited progress.