Here's What September Has Done to AMD Stock Over the Past 10 Years

September begins tomorrow, and for shareholders of Advanced Micro Devices (NASDAQ:AMD), the month arrives with a track record worth knowing. Over the past decade, September has been the chipmaker's least friendly month by a wide margin: the stock fell in eight of the past 10 Septembers, with a median decline of about 5%.

A pattern built on 10 data points deserves skepticism. But it also deserves an honest look, because the numbers say the weakness isn't entirely the market's fault.

Here's the full record, and what I'd take from it, with shares around $467 as of this writing.

Ten Septembers, eight declines

AMD fell in the Septembers of 2016 (down about 7%), 2017 (down 2%), 2019 (down 8%), 2020 (down 10%), 2021 (down 7%), 2022 (down 25%), 2023 (down 3%) and 2025 (down less than 1%). It rose just twice, jumping 23% in 2018 and 10% in 2024.

Those figures come from month-end closing prices, and AMD pays no dividend, so the price change is the whole return.

For perspective, September is not what a normal AMD month looks like. Across all 120 months of that decade, the stock's median month was a gain of about 1.6%, and 63 of the 120 finished higher. September's median was a 5% decline.

The worst of the bunch, 2022's 25% plunge, landed in a year when the stock lost more than half its value. And the best, 2018's 23% jump, capped a run that had the stock up about 200% for that year by the end of September. In other words, the extremes came in years when everything about the stock was extreme. September just happened to be along for the ride.

The market shares only part of the blame

A fair test asks how the broader market did over the same 10 months. The S&P 500 (SNPINDEX:^GSPC) fell in five of those Septembers and rose in the other five, and its median September move was roughly flat. So the index's September record is a coin flip, while AMD's is eight down months out of 10.

The overlap tells the sharper story. In the five Septembers when the market fell, AMD fell every time, and in four of the five it fell harder -- including that 25% drop in 2022, when the index lost 9%. That part is no mystery. AMD is a volatile growth stock, and it tends to amplify whatever the market is doing.

The part the market can't explain is the other half. In the five Septembers when the S&P 500 rose, AMD still declined three times. A stock that usually exaggerates the market's moves should have had more good Septembers than that.

The pattern has no mechanism behind it

So does September carry something specific for AMD? The record leans that way, but a cause is harder to find. AMD's calendar puts no earnings report in September, and no major recurring product launch lands there either. After a decade covering tech stocks, I've seen narratives built on thinner evidence than this, and most of them probably dissolve the moment you ask what would cause the pattern to repeat.

And 10 observations are just that -- 10. Strip out the 2022 plunge, and the typical September decline shrinks to less than 3%. The two up years, 2018 and 2024, show the stock is perfectly capable of a strong September when the business gives it a reason.

Notably, the month's extremes are nearly symmetrical, too. The best September (up 23%) was almost as large as the worst (down 25%). That looks like volatility, not a curse.

Ultimately, I'd read the September record as context for expectations, never as a trading signal. It says a volatile chip stock has often had a rough early fall, especially when the market wobbled. It says nothing about what the company's data center ramp or the demand for artificial intelligence (AI) computing will do over the next 30 days, and those are what move this stock.

So history gives no reason to sell a stock you own for September, and no reason to delay buying one you want. What the record does earn is patience: with a stock that has fallen in eight of the past 10 Septembers, a weak month ahead shouldn't surprise anyone -- and it wouldn't say anything about the business.

Daniel Sparks and his clients do not have positions in any of the stocks mentioned. The Motley Fool has positions in and recommends Advanced Micro Devices. The Motley Fool has a disclosure policy.