The more aggressively AI infrastructure spends money, the more the giants benefit, but valuation pullbacks can also be harsher, so don't just look at the gains.

AI stocks have surged to nearly 45% of the S&P 500's total market capitalization as of March 30, 2026, driven by massive infrastructure spending and a concentration in megacap technology leaders. According to S&P 500 data, the dominance of this "AI backbone"—tied to data center, semiconductor, and e