Nvidia and Apple now make up roughly 16% of the S&P 500 together, based on the latest index-weight read. That puts the two largest constituents back near the highest concentration levels of the modern index era.
The chart shows the combined index weight of the two largest S&P 500 constituents each year from 1980 through 2026. The early part of the series was elevated, but concentration steadily cooled through the 1990s and early 2000s before rebuilding around the largest technology platforms.
The current version of the story is unusually narrow. The two-stock peak is being driven by Nvidia and Apple, with Nvidia’s AI-driven market value joining Apple’s long-running index dominance. Together, they now represent a larger slice of the S&P 500 than many full sectors have in past cycles.
That does not make the S&P 500 broken. It does mean the index is less evenly distributed than the name suggests, and the largest companies now have more influence over benchmark returns, ETF flows, and passive portfolios.