How AI and Big Tech Came to Dominate the S&P 500
Feb 27th 2026
A handful of highly profitable tech companies tied to artificial intelligence now account for a growing share of the S&P 500, concentrating value and increasing market risk.
- Tech now represents about 32 percent of the S&P 500, roughly $20 trillion of a $63 trillion total.
- The five largest U.S. public companies make up almost a third of the index and are all highly profitable tech-linked firms.
- Nvidia alone was worth about $4.5 trillion, more than double the combined value of the entire energy sector and larger than materials, utilities and real estate combined.
- The top 10 companies account for nearly 40 percent of the S&P 500, concentrating market risk and raising volatility concerns.
- Tech made up 26 percent of the index in 1999 and 14 percent in 2007, and AI-driven spending on data centers plus expected AI IPOs could push concentration even higher.