Earnings season usually belongs to hundreds of companies at once. This time, two chipmakers could steal most of the show.

Nvidia (NVDA) and Micron (MU) are expected to deliver more than a third of the S&P 500’s earnings-per-share growth for the third quarter, according to a ZeroHedge analysis of Goldman Sachs and FactSet estimates, Yahoo Finance reported. For anyone who owns an index fund, that makes two stocks unusually important this fall.

Nvidia alone can move the whole market. Ahead of its last report in August, options traders were pricing in a stock move worth more than $280 billion in market value.

And because the company makes up such a large slice of the major indexes, that swing reaches far beyond its own shareholders. Analysts had expected about $92 billion in quarterly revenue going into that report.

Also read: Micron just sent a stark memory chip warning to tech stock investors

Nvidia and Micron are carrying the index

Goldman Sachs has done the math. AI infrastructure companies are expected to account for more than half of the index’s third-quarter earnings growth, with Micron and Nvidia alone delivering more than a third. The firm also expects most companies to beat their estimates.

The gap with the rest of the market is striking. The two semiconductor giants are on track to generate more earnings growth than the bottom 490 companies in the S&P 500 combined, as reported by Yahoo Finance. Those companies make up the vast majority of the index by count.

That leaves the index unusually top-heavy. About two-thirds of expected earnings growth comes from just 10 companies, while the median company in the S&P 500 is growing far more slowly.

The overall numbers still look strong. The S&P 500 is expected to post earnings growth of 29.5% for the third quarter, which FactSet says would be the eighth consecutive quarter of double-digit growth, according to Yahoo Finance.

Nvidia and Micron are expected to deliver more than a third of the S&P 500’s earnings-per-share growth for the third quarter.

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Micron’s own memory boom

Micron set the tone just before the quarter ended. On Sept. 30, the memory maker beat earnings estimates and issued strong guidance, with data center revenue accounting for 40% of total quarterly sales, as reported by Yahoo Finance.

The details were just as eye-catching. Quarterly revenue rose nearly fivefold from a year earlier, the company’s outlook for the next quarter came in well above Wall Street’s forecasts, and Micron said most of its 2027 output is already committed to customers. It now has 26 long-term agreements with customers, up from 16, TheStreet reported.

The demand is coming from AI data centers, which are buying up most of the available memory supply. The shortage is expected to last until the end of 2028, and device makers such as Apple and Samsung are paying more for chips, part of which is being passed on to shoppers.

Strong results do not always lift the shares, though. Micron’s stock fell after a solid report and a bullish outlook in June. Around the same time, Jeff Jacobson of 22v Research warned that the price momentum factor had become a very crowded trade, a warning that applies squarely to Micron and the AI memory trade.

Nvidia’s next act

Nvidia’s last report showed how far ahead it still is. For its fiscal second quarter, reported on Aug. 26, revenue rose 106% from a year earlier to $96.2 billion, with data center sales making up the bulk of it. Net income for the quarter came to nearly $60 billion.

The outlook went even further. Nvidia guided to about $108 billion in revenue for the current quarter, its first ever above $100 billion, and gave a first look at fiscal 2028 with growth of about 70%. Management also pointed to a cloud industry backlog above $2 trillion.

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Demand is not what is holding it back. Chief Financial Officer Colette Kress said the company expects supply to remain a bottleneck at least through the end of fiscal 2028, with memory pricing a key pressure point. 

Wall Street bulls think the buildout has a long way to run. Dan Ives of Wedbush Securities said AI is in the third inning of a nine-inning game. He named Nvidia a top pick.

What could possibly go wrong

Some see warning signs inside the good news. Micron’s adjusted gross margin of 87% is so wonderful until you consider what other manufacturers do when margins reach 87%: they build, according to Forbes. New plants could also start producing just as competitors expand too.

Nvidia has flagged its own pressure points. The company said it is capacity constrained and pointed to extreme pricing conditions in memory, and it expects lower gross margins over the next two quarters. Jensen Huang said fiscal 2028 would be a lot higher without those limits.

For now, analysts expect the run to continue, with earnings growth of 27.6% forecast for the fourth quarter and 32.4% for all of 2026. When two companies carry this much of the load, though, any stumble from either one would be felt across the entire index. Investors will find out soon whether the forecasts hold up.

Related: Micron’s memory boom faces a new test