S&P 500 Rally Excluding AI Enablers Flat Since Late February, Goldman Says

The S&P 500’s 10% gain since late February masks a thinning rally almost entirely dependent on artificial intelligence-linked stocks, according to Goldman Sachs. An index that strips out AI enablers is slightly lower over the same period, while a basket of AI winners has surged more than 45%. Bianco Research found that 41 AI-related stocks tracked by JPMorgan now account for nearly half of the S&P 500’s market value — a concentration not seen around a single theme in 150 years, comparable to the railroad boom of the late 19th century. Jim Bianco called the situation “probably a bubble” but warned timing an exit is treacherous, noting that investors who sold after Alan Greenspan’s 1996 “irrational exuberance” warning missed a nearly 300% Nasdaq rally before the dot-com peak. As long as AI leadership persists, the headline index can appear robust. If those stocks falter, the S&P 500 may have little else propping it up.