The largest companies in the S&P 500 are seeing their market weight surge faster than their actual earnings — a growing imbalance that’s starting to raise eyebrows on Wall Street.

Lori Calvasina, head of U.S. equity strategy at RBC Capital Markets, has often dismissed talk of an AI-fueled market bubble. Yet in her latest report shared with MarketWatch, she pointed to one chart that’s giving her some concern.

It compares the top 10 stocks’ weighting in the S&P 500 to their share of total corporate profits. According to Calvasina, those companies now make up more than 44% of the entire index — the highest level since at least 1990 — while accounting for just 34.3% of total net income. That nearly 10-point gap echoes levels seen at the height of the dot-com bubble in 2000.

“While we haven’t agreed that the market is in an AI bubble like the old TIMT era, the risk has definitely grown,” she said, referring to the Technology, Internet, Media, and Telecommunications boom that preceded the early 2000 crash.

The top 10 stocks — including Nvidia, Meta, Broadcom, Microsoft, Amazon, Alphabet (both share classes), Apple, Tesla, and Berkshire Hathaway — dominate the AI narrative. Apart from Berkshire, all are deeply tied to the technology driving the latest market enthusiasm.

This trend isn’t entirely new. Since 2021, the biggest companies’ market weight has consistently grown faster than their earnings share, fueled by investor optimism about long-term AI-driven growth — especially since ChatGPT ignited the frenzy in late 2022. But lately, that gap has been widening even faster.

The imbalance has resurfaced bubble talk, particularly after recent earnings from AI heavyweights. Meta’s stock plunged last week, wiping out over $200 billion in market value as investors balked at its expanding AI spending plans. Still, strength from other tech giants — most notably Amazon — has helped offset the declines.

Amazon’s latest deal to provide cloud power to OpenAI added fresh fuel to the market rally as November began. By Monday’s close, the S&P 500 and Nasdaq finished higher, while the Dow and Russell 2000 slipped modestly — a reminder that Wall Street’s momentum remains powered by its biggest, most AI-focused names.