No single stock has shaped the S&P 500's returns over the past five years the way Nvidia has. The chipmaker has added more than 10 percentage points to the index's 84% total return since 2021, more than any other stock by a wide margin, according to The Kobeissi Letter. That single-stock contribution works out to roughly 12% of the S&P 500's entire five-year gain — and more than double Apple's contribution over the same period.
Independent data tracking contributors to the index's return, compiled by Statista, corroborates just how concentrated the market's gains have become in a small handful of mega-cap technology names, with Nvidia consistently ranked at or near the top of that list.
A Rally Still Being Driven by the Same Names
The concentration hasn't eased in 2026. Nvidia and Micron have been singled out as the two stocks primarily responsible for driving the S&P 500's 2026 rally to fresh record highs, extending a pattern where AI infrastructure and semiconductor names continue to carry a disproportionate share of the index's performance relative to the other roughly 495 constituent companies.
What Concentration Risk Means for Index Investors
For anyone holding a broad S&P 500 index fund, Nvidia's outsized weight means the fund's returns are far more tied to one company's fortunes than the “diversified 500 stocks” framing suggests. A double-digit percentage-point swing in Nvidia's own performance can move the entire index's return meaningfully on its own, a dynamic that cuts both ways: it has powered years of index outperformance, but it also means any sharp reversal in AI-sector sentiment — the kind that has already rattled other market participants this year — carries outsized weight for anyone assuming index exposure spreads that risk evenly.
Kobeissi's figures underscore just how much of the market's recent story is really a story about a handful of AI infrastructure winners, Nvidia chief among them, rather than broad-based corporate earnings growth.
