The Warning Signs Flashing From the Tech-Heavy Bloat of the S&P 500

[https://www.nytimes.com/interactive/2026/02/26/business/stock-market-sp-500-nvidia-tech-bubble-crises.html](https://www.nytimes.com/interactive/2026/02/26/business/stock-market-sp-500-nvidia-tech-bubble-crises.html) To understand how abnormal and worrisome this moment might be, The New York Times analyzed data from S&P Dow Jones Indices that compiled the market values of the companies in the S&P 500 in December 1999 and August 2007. Each date was chosen roughly three months before a downturn to capture the weighted breakdown of the index before crises fully took hold and values fell. The companies that make up the index have periodically cycled in and out, and the sectors were reclassified over the last two decades. But even after factoring in those changes, the picture that emerges is a market that is becoming increasingly one-sided. In December 1999, the tech sector made up 26 percent of the total. In August 2007, just before the Great Recession, it was only 14 percent. Today, tech is worth a third of the market, as other vital sectors, such as energy and those that include manufacturing, have shrunk. In December 1999, Microsoft was the most valuable tech company in the months leading up to the dot-com bubble bursting. Cisco was second; it now ranks at number 32 on the S&P 500.