The S&P 500's reliance on a handful of tech giants has hit an all-time high, sparking concerns that a stumble in the sector could send the broader market into a tailspin.
The technology sector now represents 39.4% of the index's market capitalization, according to LSEG Datastream. That tops the previous record set during the 2000 Internet bubble, when the sector accounted for roughly 35%.
"If the small number of tech stocks leading this market higher roll over, by definition, the indexes are going to roll over," said Matthew Maley, chief market strategist at Miller Tabak. He warns that when the indexes turn down meaningfully, money flows inevitably reverse.
The outsized influence is driven by the massive build-out of AI infrastructure. Since the market's March low, the tech sector has soared 47%, more than doubling the broader S&P 500's gain. Semiconductor stocks have led the charge, with shares of Micron surging 230%, and Intel and Advanced Micro Devices each gaining over 160%.
Yet the rally is remarkably narrow. Only about 60% of S&P 500 stocks are trading above their 200-day moving average, well below the approximate 73% level historically seen when the index is at new highs. "This is pretty characteristic of the bull market we've been in," noted Adam Turnquist, chief technical strategist at LPL Financial, describing the breadth as "underwhelming."
For investors, the key difference between today and 2000 is profitability. The tech sector accounts for more than a quarter of trailing 12-month net income among S&P 500 members-nearly double its share at the peak of the dot-com bubble, according to Bespoke Investment Group.
"It's not clear that earnings growth can keep up with what the market is pricing in," Bespoke said in a note. "But in terms of profitability, this latest surge in market cap share looks much more sustainable."
Despite the strong earnings support, strategists urge caution. "The way they're performing is like you're driving a race car at 200 miles an hour," said Walter Todd, chief investment officer at Greenwood Capital. "It doesn't take much to cause an accident at that speed."