After starting the week strong, Micron (MU 6.78%) stock tumbled an unlucky 7.7% through 10:55 a.m. ET.
Blame Samsung for that.
Image source: Micron.
Korea sends the semi market South
South Korean technology giant Samsung reported its Q2 2026 earnings last night. The news was objectively good -- sales up 28% sequentially, and more than double last year's Q2 revenue. Operating profit surged 19-fold, rising to $58.4 billion.
And yet Samsung stock sold off 7% today. Why?
The results beat analyst forecasts, but in a quirk of this overheated artificial intelligence-fueled stock market, investors expected Samsung to beat expectations. This triggered a "buy the rumor, sell the news" phenomenon in which investors sold Samsung stock despite its numbers being better than "expected" -- and despite Samsung confirming computer memory prices are still rising, and its profits are continuing to climb.
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Key Data Points
What this means for Micron stock
So how does all of this affect Micron, and why is it sparking a sell-off today?
Well, consider: Samsung is the world's biggest supplier of DRAM computer memory, used to make high-bandwidth memory (HBM) used in AI data centers. It's got a 38% share of the global market. SK Hynix, No. 2 in DRAM, is No. 1 in HBM with more than a 50% market share. Micron makes both NAND and DRAM memory, and its DRAM share is smaller -- about 22%, still enough for third place.
If things stay as they are, with prices rising and demand insatiable, Micron should do quite well. The problem is alongside announcing powerful profits, Samsung also said that it is building "massive semiconductor fabrication plants" to add supply to the market -- growing its market share, eating away at Micron's, and potentially closing the supply demand gap in the process.
This, in a nutshell, is why Micron stock is selling off today.
