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October 19, 2026Seagate · STX · Western Digital · WDC5 min read

Seagate lost nearly a third of its value in two weeks. The first push came from Toshiba.

From October 1 to October 16, Seagate fell 32.4% and Western Digital 28.2%. The last week looked like part of a chip selloff. The doubt behind it had a name two weeks earlier.

What happened

In the week of October 12, Seagate (STX) fell from its October 9 close of $783.00 to $639.01, down 18.4%. Western Digital (WDC) fell from $397.28 to $332.00, down 16.4%. The worst day was the last one. On Friday, October 16, Seagate fell 7.5% and Western Digital 6.9%.

That week, most of the chip sector was falling with them. But these two had already lost a lot before it started. On October 1, Seagate closed at $945.57 and Western Digital at $462.56.

October 1 → October 16, 2026
Two hard-drive makers, two drops
−32.4%Seagate (STX), $945.57 → $639.01
−28.2%Western Digital (WDC), $462.56 → $332.00
5 daysOct 12–16 alone: STX −18.4%, WDC −16.4%
Daily closing prices

To see why, you need to know what these companies sell. AI data centers keep enormous amounts of data, and most of it still sits on high-capacity hard drives, because they cost far less per terabyte than flash. Only three companies make those drives: Seagate, Western Digital and Toshiba. When demand outran supply, Seagate and Western Digital could charge more. Investors paid up for that shortage. The risk to a shortage is simple: someone builds more.

The first drop had a name

On October 2, both stocks fell 10.2% in a day. MarketWatch's headline asked why Western Digital and Seagate were seeing big drops. The answer was Toshiba, which planned to add a lot more hard-drive capacity. Another headline that day put the worry plainly: investors feared the hard-drive shortage would ease.

On October 5, MarketWatch reported that analysts were playing the Toshiba threat down, and both stocks bounced. Seagate rose 4.5% and Western Digital 6.3%.

The bounce lasted one day. On October 6, 24/7 Wall St. reported that Toshiba's expansion was hitting the group again. Seagate fell 9.2% and Western Digital 6.9%. The same headline noted that Micron, which makes memory chips rather than drives, held flat. This was a hard-drive story, not a chip story.

The app I build, Loom, links each news story to the stocks it's likely to affect. It put all four Toshiba stories next to both Seagate and Western Digital, including the one where analysts said the worry was overdone. Reading them in a row is what made me see October 6 as the same doubt coming back, not a new one. Loom's line on the second story was: "Toshiba capacity doubling threatens the hard-drive shortage premium Seagate and WD have enjoyed."

By October 9, Seagate was at $783.00 and Western Digital at $397.28. Seagate was already down 17.2% from October 1, and Western Digital 14.1%, before the week everyone noticed.

Then the whole sector fell

The week of October 12 brought new worries, and none of them were about hard drives.

On October 12, memory stocks slid after China's CXMT described a denser DRAM chip design. 24/7 Wall St. reported Micron and SK Hynix down 4% and Western Digital down 2%. On October 13, chip stocks fell as the chief executives of Broadcom and Intel raised doubts about AI funding. MarketWatch called the Broadcom chief's "gamblers" comment a storm, and the Financial Times later reported he had warned of a "casino" mentality in AI investing. By October 15, Bloomberg reported SK Hynix down 57% from its peak as the selloff deepened, and CNBC said memory stocks were being hammered over China and a possible oversupply by 2029.

Daily close, indexed to 100 on October 1
A Toshiba drop, a one-day bounce, then the sector selloff
6070809010012345Oct 1Oct 6Oct 12Oct 19
Seagate (STX)Western Digital (WDC)
  1. 1Oct 2Toshiba plans more hard-drive capacity. Both fall 10.2%.
  2. 2Oct 5Analysts play the threat down. STX +4.5%, WDC +6.3%.
  3. 3Oct 6Toshiba's expansion hits the group again. STX −9.2%, WDC −6.9%.
  4. 4Oct 12China's CXMT shows a denser DRAM design. Memory stocks slide.
  5. 5Oct 13Broadcom and Intel chiefs raise doubts about AI funding.
Daily closing prices, Oct 1 – Oct 19, 2026. Shaded: the week of October 12.

I didn't find a story that week about hard-drive supply itself. Seagate and Western Digital fell because the group fell. But they went into that week with their main support, the shortage, already in question.

The other side

This wasn't a straight line down. Between October 1 and October 9, the low was $774.83 for Seagate and $393.31 for Western Digital, and the bounce on October 5 showed real buyers who thought the Toshiba fear was overdone. That was a reasonable view, and the analysts who held it may still be right. Adding capacity takes time.

The selloff also stopped. On Monday, October 19, Seagate rose 3.4% to $660.81 and Western Digital 6.1% to $352.21.

What I take from it

A bounce on reassurance is not the same as an answer. On October 5, the Toshiba question was argued down, not settled, and the stocks gave back the gain the next day. When the sector turned a week later, the two stocks whose premium rested on a shortage had less to hold them.

It was a bad week across the AI trade. The same week, CoreWeave's bonds broke, for different reasons. The common thread was that investors started asking which parts of the AI build-out were priced for things going right for a long time.

Sources

Prices are daily closes. This is not investment advice.

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