Tech Now Makes Up 39.4% of S&P 500 Market Value, Above the Dot-Com Era Peak

Technology's footprint in the S&P 500 has returned to levels last seen in March 2000. The information technology sector now represents 39.4% of the index's total market capitalization, surpassing the prior dot-com bubble high of nearly 35%. The concentration looks even more extreme once large-cap names outside the formal IT bucket are included. Factoring in major AI spenders such as Alphabet, Amazon, and Meta pushes the combined share to more than 50% of the S&P 500's total market value. Behind the run-up Since the S&P 500 bottomed in March 2026, the IT sector has climbed about 47%, outpacing the broader rebound and driving much of the index's gains. Semiconductors have led the charge. Micron is up 230% from the March low, while Intel and AMD have each advanced more than 160%. The sector's earnings weight has also risen sharply. IT now generates over 25% of the S&P 500's trailing 12-month net income, nearly twice its share of profits in Q1 2000, when valuations were fueled far more by speculation than cash flow. Why AI is amplifying the concentration AI investment has become a corporate arms race, lifting the entire ecosystem from chip makers and designers to cloud platforms and data-center operators. That spending wave helps explain how the index moves from roughly 39% in IT alone to above 50% when the broader AI complex is counted. What investors should watch Miller Tabak's Matthew Maley has warned that the market could be vulnerable if leadership in the largest technology stocks falters. With roughly half of the index tied to one crowded trade, even a modest rotation away from tech could translate into an outsized decline for the S&P 500 overall. History offers a reminder: investors who bought the index at the dot-com peak in March 2000 waited more than a decade to get back to breakeven. Today's setup is supported by real earnings rather than promises, but the concentration risk may be even higher. A single sector approaching 40% of index value is largely unprecedented. For passive investors, the implication is straightforward: holding an S&P 500 index fund now effectively means taking a large, often unintentional, bet that technology will continue to outperform.