Three Stocks Are Now 21% of the S&P 500, the Most Ever

NVIDIA, Apple, and Microsoft now dominate the S&P 500 at a concentration level that makes the 1980s tech giants look like small players, and what that means for anyone holding an index fund is more unsettling than most realize.

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At the close on October 6, 2026, the S&P 500 finished at a record 7,818.93, up 0.58%. Three companies now account for an unusually large share of that level.

All three moved modestly on the session. NVIDIA rose 0.14% to $239.24 after touching an intraday record of $243.37. Apple gained 0.22% to $333.63, and Microsoft added 0.78% to $529.30.

The concentration record came from months of steady gains. NVIDIA is up 28.58% year to date, and Apple is up 23.06%. The SPDR S&P 500 ETF Trust (NYSEARCA:SPY) is up 14.25% over the same stretch. If you own an S&P 500 index fund, more than a fifth of your money sits in three companies, stretching the usual meaning of diversification.

The over 21% figure describes the index itself. SPY’s own holdings, dated the prior session, show NVIDIA at 8.63%, Apple at 7.25% and Microsoft at 5.82%. That is a combined fund holdings weight of 21.70%, and the top ten holdings add up to 39.27%.

A cap-weighted index sizes each company by market value, so its biggest winners keep gaining weight as they grow. This means the index acts like a momentum strategy even though it is passively managed.

NVIDIA, worth about $5.78 trillion, reported fiscal second-quarter revenue of $96.22 billion, up 105.8%. Data Center sales made up $89.02 billion of that, and the company guided third-quarter revenue to $108.0 billion.

Apple, at about $4.87 trillion, posted fiscal third-quarter revenue of $109.42 billion, up 16.4%. However, management called memory pricing a “100-year flood” for its hardware costs.

Microsoft, at about $3.93 trillion, reported fiscal fourth-quarter revenue of $90.01 billion. Azure passed $100 billion in annual revenue, and commercial signed backlog rose 84% to $678 billion.

Only 25% of S&P 500 stocks trade above their 50-day moving averages. Most of the index sits below its own recent trend even as the index hits a record.

Thin breadth like this can last a while. The picture likely changes only when lagging stocks begin rising, or the three leaders start to decline.