The S&P 500 (SNPINDEX:^GSPC) has climbed around 12% in 2026 as of this writing, not counting dividends. But three of the index’s five biggest companies have trailed. Microsoft (NASDAQ:MSFT) is up around 8% this year, Amazon (NASDAQ:AMZN) is up about 7%, and Alphabet (NASDAQ:GOOGL)(NASDAQ:GOOG) is up about 2%, based on its Class A shares.
These three make up about 15% of the index. And they all report quarterly results within two days of each other. Microsoft and Alphabet are scheduled for Wednesday, Oct. 28, and Amazon follows on Thursday, Oct. 29.
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For anyone with an S&P 500 fund, those reports are arguably the biggest scheduled test left in the fund’s year. Yet this year’s 12% rise has needed surprisingly little from these three stocks.
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The index hasn’t needed them
At the end of 2025, Microsoft, Amazon, and Alphabet’s two share classes made up around 15.6% of Vanguard’s S&P 500 index fund, according to the fund’s annual report. This was slightly more than Nvidia (NASDAQ:NVDA) and Apple (NASDAQ:AAPL), which had around 14.6% together.
The two groups have done very different things for the index, though. By my math (weighting each stock’s gain this year by its share of the fund at the end of 2025), Apple and Nvidia added around 3 percentage points to the index’s 12% rise, with Apple up about 28% and Nvidia about 14% as of this writing. The three laggards added about 1 point in all. Even Micron Technology and Advanced Micro Devices, which together started the year at just above 1% of the fund, contributed nearly 2 points, as Micron’s shares tripled and AMD’s more than doubled.
In other words, if the three laggards had simply matched the index this year, an S&P 500 fund would’ve gained almost 13% instead of 12%.
The fund’s weights have already changed, of course. Nvidia and Apple now make up about 15.5% of the index, but Microsoft, Alphabet, and Amazon have dipped to about 15%.
How much could the reports move an S&P 500 fund?
Each of the three stocks has moved around 10% or more the day after at least one of its reports in 2026.
Microsoft dropped about 10% the day after its fiscal second-quarter report in January, then jumped about 16% after its fiscal fourth-quarter report in July. Alphabet’s Class A shares climbed around 10% after the company’s first-quarter results came out in April, and they fell about 7% following its second-quarter results in July. And Amazon slid about 6% after its fourth-quarter report in February before soaring about 15% when it reported in July.
