S&P 500’s Rare Split Screen: Mega-Caps Melt Down as the Broader Yard Boils

The S&P 500 closed on November 2 more than two standard deviations below its 50-day moving average while 46.8% of its constituent stocks were overbought, marking an unprecedented divergence in 36 years of index data, according to Bespoke Investment Group.

Since 1990, five similar market conditions have occurred, with overbought stocks accounting for no more than 33.4% of the index. The unusual split reflects the S&P 500’s weighting structure, which gives larger companies greater influence over its performance. Sharp declines in Nvidia, Alphabet and Meta can therefore pull down the index even as hundreds of other constituent stocks rise.

October data showed that divergence in action. The regular S&P 500 fell 0.9%, while its equal-weighted counterpart gained 5%, producing a 5.9-percentage-point gap that was the widest since April 2009. Nine of the 11 sectors advanced as investors questioned the returns on massive AI spending, according to Nasdaq’s October 2026 review.

The rotation favored companies outside the AI trade. Energy producers Chevron and ConocoPhillips could attract further investment if oil prices remain supportive, while healthcare companies including Eli Lilly and Johnson & Johnson may benefit from demand for more dependable earnings. Consumer staples stocks such as Walmart could also gain attention as investors reduce exposure to expensive technology shares.

October’s gains have already increased the risk of a reversal, leaving attention on whether the rotation can persist long enough to support a broader stock market rally or whether weakness in Big Tech eventually spreads elsewhere.