The S&P 500 has climbed roughly 12% in 2026, offering strong returns for index fund investors. However, a closer look at the data reveals a surprising market dynamic: the average company in the index is not keeping pace with the headline numbers.
What Happened to the Average Stock?
For most of the year, the typical stock outperformed the broader market. At the end of August, the S&P 500 Equal Weight Index—which gives every company the same influence—was up about 14%, comfortably ahead of the standard market-value-weighted index.
That dynamic shifted dramatically in September. While the standard S&P 500 dipped just 0.5%, the equal-weight index slid 5%. Roughly three-quarters of the individual stocks in the index dropped during the month.
The overall index managed to stay afloat only because massive gains from a handful of mega-cap companies masked widespread market weakness. In fact, roughly half of the companies in the index at the start of 2026 are actually down for the year.
The Four Stocks Powering the Rally
The entire market narrative comes down to four major tech and semiconductor players: Nvidia, Apple, Micron Technology, and Advanced Micro Devices (AMD).
Nvidia and Apple started the year with heavy index weights and have posted steady gains of around 24% and 22%, respectively. Meanwhile, the real fireworks came from memory chipmaker Micron—whose stock has nearly quadrupled with a 285% surge—and AMD, which climbed roughly 188%.
Combined, these four stocks account for about 6 full percentage points of the S&P 500's 12% total gain. Essentially, half of the index's dollar returns this year came from this elite quartet, while the remaining 84% of the fund's holdings averaged a modest 7% gain.
What's Next for Investors?
This heavy reliance on a few chip giants highlights how standard market-cap indexes operate. As winners grow, they automatically claim a larger slice of the fund.
While this structure successfully captures top performers during a bull run, it also introduces concentration risk. If these semiconductor and tech leaders experience a pullback, the broader S&P 500 will feel the impact much more acutely than the average standalone business.
