Deutsche Bank strategist Bankim "Binky" Chadha warns the S&P 500 has become overly dependent on a handful of mega-cap stocks. This concentration increases market vulnerability as tech dominance skews index performance.

Chadha's concern reflects growing unease about valuation gaps between market leaders and broader equities. Narrow breadth has characterized recent gains, with five stocks driving most S&P returns. This creates fragile foundations for sustained rallies.

Investors should consider sector diversification as bond markets and interest rates shift, Chadha suggests. Rotation strategies may outperform passive indexing. Market participants are watching for breadth expansion signals.

Strategists point to historical parallels when excessive concentration preceded corrections. Current valuation premiums for mega-caps appear stretched. Portfolio managers may reallocate toward undervalued sectors if momentum fades.