TLDR:
42 AI stocks generated 67% of S&P 500 price returns since January 2024, according to reported figures.
AI companies accounted for 58% of S&P 500 earnings growth over the reported period, according to data.
AI-related companies drove 81% of combined capital expenditure and R&D growth across the S&P 500.
Only 29% of stocks outperformed the S&P 500 over the previous three years, indicating narrow market breadth.
A group of 42 artificial intelligence (AI) stocks generated 67% of the S&P 500’s price returns since January 2024, exposing the index’s growing dependence on a relatively small group of companies.
Figures shared by The Kobeissi Letter on October 11, 2026, and attributed to Bloomberg and JPMorgan, show that these companies also accounted for 58% of earnings growth and 81% of combined capital expenditure (CapEx) and research and development (R&D) growth.
The gap between AI names and the rest of the market is historic:
Since the start of 2024, a basket of 42 AI stocks has generated 67% of the S&P 500’s price return.
In other words, those names have contributed +22 percentage points to the index’s +33% gain over this period.
By… pic.twitter.com/InTh04i0so
— The Kobeissi Letter (@KobeissiLetter) October 11, 2026
The remaining 458 companies contributed 11 percentage points to the index’s price returns, compared with 22 percentage points from the AI group. The figures reveal how market performance and corporate spending have become increasingly concentrated among technology-related businesses.
AI Stocks Dominate Returns and Corporate Spending
The concentration extends beyond share prices. The 42 companies accounted for more than half of earnings growth and over four-fifths of additional spending growth across the index. Much of this spending supports data centers, advanced semiconductors and computing infrastructure required to develop and operate AI systems .
Research and development commitments also contribute to the gap between these companies and the broader market. A separate report from JPMorgan Private Bank’s Eye on the Market Outlook 2026 found that 42 AI-related companies represented approximately 65% to 75% of S&P 500 earnings, revenues and capital spending since ChatGPT launched in November 2022.
However, that analysis covers a longer period and uses different measurements from the figures shared by The Kobeissi Letter. Both sets of data point to the substantial role these companies play in corporate performance. Recent earnings figures further illustrate the concentration.
JPMorgan Asset Management reported in August 2026 that just 10 companies accounted for 77% of expected second-quarter earnings growth. Semiconductor companies drove much of that growth, while heavy infrastructure spending continued to pressure profitability at some major cloud and technology businesses.
Narrow Market Breadth Leaves the S&P 500 Dependent on AI Leaders
The concentration matters as the S&P 500 represents hundreds of companies, yet its overall performance can rely heavily on a limited number of large constituents. Reuters reported on October 9, 2026, that the U.S. bull market remained largely driven by AI-related investments .
The index had gained 117% since its October 2022 low, although rising Treasury yields, interest rates and concentration concerns threatened the rally. The Kobeissi Letter also reported that only 29% of stocks had outperformed the benchmark over the previous three years.
This limited market breadth indicates that index gains have not translated into comparable performance across most constituents. The figures do not establish whether current valuations are justified or predict future returns.
However, they identify a measurable dependence on a narrow group of companies for price performance, earnings expansion and corporate spending. The central issue remains whether continued AI investment will translate into sufficient revenue and productivity gains to support sustained business performance across the sector.
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