Nearly 40% of S&P 500 in Bear Market as Index Concentration Masks Underlying Weakness

What’s happening

Nearly 40% of S&P 500 constituents are in bear market territory, down 20% or more from recent highs, even as the index itself trades near record levels. The divergence reflects extreme concentration in mega-cap technology stocks that are masking broad-based weakness across the market.

Market impact

The breadth deterioration is a warning sign that the rally is fragile and dependent on a narrow set of AI-related mega-caps. If these leaders falter—as CoreWeave's distress suggests is possible—the index could face significant downside as the hidden weakness becomes visible.