AI Stocks Now Drive Most S&P 500 Gains

Big Tech's $720 billion data center buildout is tying index returns to whether AI spending pays off.

Updated on Nov. 2, 2026 in Artificial Intelligence

Isometric editorial illustration of a tall, dense column of dark rack modules with parallel cables running down one side, in oxblood, slate and mustard on cream. — Big Tech's $720 billion data center buildout has made AI-linked stocks responsible for about 60% of S&P 500 gains in the period examined. AI Illustration. Upload story photo >

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Do you think the stock market is getting riskier because of AI spending?

An analysis of 47 AI-related stocks found they accounted for about 60% of S&P 500 gains in the period examined, with roughly 75% of gains in the first half of 2026. These are market-performance figures for existing public companies, not a new product or research result.

Why it matters

The concentration of index gains in AI-linked stocks shows how heavily the broader U.S. market now depends on spending by a few large technology companies on data centers and chips. Because the top 10 companies make up roughly 40% of the S&P 500's total market value, a pullback in AI spending or demand could affect the index as a whole.

The analysis covers 47 AI-related stocks and reported capital spending by four companies, with the share of index gains and market value as the main measures. The figures describe market concentration and planned investment, not measured returns on AI systems, and the source does not state how spending translates into revenue.

The players

Amazon

Amazon operates Amazon Web Services, its cloud computing division, which reported a 39% sales increase to $46 billion and is central to its AI infrastructure spending.

Microsoft

Microsoft is a major cloud and software company whose data center and AI capital spending is among the four Big Tech outlays driving this year's investment total.

Google

Google, owned by Alphabet, is among the four large technology companies planning data center and capital spending of more than $720 billion this year.

The details

The spending counted here covers computer chips, servers, data centers and the wider infrastructure needed to run AI systems. Free cash flow, the cash a company has left after paying operating costs and capital investments, is a key measure in this picture, and most of the companies are spending more on data centers than they generate from operations. That gap means the buildout is being funded beyond what the core businesses currently produce.

During the first half of 2026, AI-related stocks accounted for roughly 75% of the S&P 500's gains.
In the second half of 2026, AI-related stocks began weighing on the S&P 500's performance.
On Friday, October 30, 2026, the Nasdaq fell 2.9% and the S&P 500 dropped 1.8%.
Amazon, Microsoft, Google and Meta are expected to spend even more on AI in 2027.

The Tech Race

Amazon, Microsoft, Google and Meta are competing to build AI infrastructure at a scale that has roughly tripled their spending over two years. The market's reliance on this race is now visible in how much of the S&P 500's gains come from AI-linked stocks.

Shareholders in index funds and retirement accounts tied to the S&P 500 are directly exposed to how these AI-linked stocks perform. Consumers and businesses using cloud services will see the effects of the data center buildout first in the capacity and pricing of the platforms that host them.

The takeaway

Watch whether the planned spending of more than $720 billion is sustained in 2027, since expectations for that year are already higher. A reported slowdown in AI demand or a further decline in AI-linked stock performance would be the first sign that the market's dependence on this buildout is shifting.