The 15 largest S&P 500 stocks now account for 46.7% of the index's value, a record high compared to 27.2% in the Dot-Com Bubble.
The Kobeissi Letter noted that the top 15 stocks in the S&P 500 now hold a record 46.7% of its total market value, with the remaining 485 companies accounting for 53.3%.
That figure is 19.5 percentage points higher than the 27.2% that the same group accounted for during the 2000 Dot-Com Bubble.
Nvidia (NVDA) tops the list with a 7.5% weighting, while Apple (AAPL) stands at 7.1%, Alphabet (GOOGL) at 5.9%, and Microsoft (MSFT) at 5.6%.
The four stocks combined represent 26.1%, and the next 11 positions account for roughly 20.6%.
At the same time, the 434 smallest stocks have a combined value that approximately equals that of the five largest, marking the widest gap on record.
BREAKING: The 15 largest S&P 500 stocks now account for a record 46.7% of the index’s market value.
— The Kobeissi Letter (@KobeissiLetter) October 21, 2026
By comparison, during the 2000 Dot-Com Bubble, the 15 largest stocks accounted for 27.2% of the S&P 500.
The remaining 485 stocks represent just 53.3% of the S&P 500’s market… pic.twitter.com/7Z6biUxGVP
Because the S&P 500 indexes companies by market capitalisation, an increase in their stock prices automatically raises the weight of the biggest firms.
Economist Peter Schiff, in his bear market warning, pointed out that 479 US stocks were trading at 52-week lows.
Separately, Goldman Sachs has indicated that the index is being supported by shares in the artificial intelligence (AI) sector.
Looking at past performance, the S&P 500 fell roughly 50% from its March 2000 high, making that period a logical benchmark for comparison.
According to Goldman, market breadth — the extent to which gains are distributed across stocks — is at its narrowest since the dot-com bubble.
Investor Michael Burry’s market warning references the 2000 and 2008 periods, where initial strength was followed by more severe declines. He describes the current sentiment as denial and forecasts it will persist for six to nine months.
By contrast, Tom Lee, co-founder of Fundstrat Global Advisors, views the AI situation as comparable to 1997, not 1999. His model projects a bubble peak around 2033, which remains several years off.
As a result, S&P 500 index funds now allocate nearly half of their assets to just 15 companies. The index, often viewed as a representation of the US economy, is increasingly following the performance of a limited number of mega-cap stocks.
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