KOSPI Plunges 3.6% in Seoul: Samsung and SK Hynix Fall 5% as AI Fears Return

South Korea's KOSPI plunged as much as 3.59% on Tuesday, November 3, wiping out Monday's rebound in a single morning, as Samsung Electronics and SK hynix both fell around 5%. The selloff in Seoul followed another slide in U.S. technology stocks overnight, renewed doubts about whether massive AI spending will pay off, and caution ahead of voting in the U.S. midterm elections.

What happened in Seoul?

The KOSPI opened at 5,715.19, down 143.89 points or 2.46% from Monday's close of 5,859.08, according to the Korea Exchange. It kept falling: down 2.91% at 5,688.65 by 9:02 a.m., down 3.36% at 5,662.37 by 9:15 a.m., and down as much as 3.59% to 5,649.03 in early trading. By around 9:30 a.m. it stood at 5,682.59, down 3.01%.

The smaller KOSDAQ also fell, opening down 1.42% at 723.92 and sliding 2.56% to 715.54 in early trade.

That reversal matters because Monday had looked like a recovery. The KOSPI had staged a V-shaped rebound on November 2, turning an early fall into a strong close at 5,859.08. Tuesday's open erased that gain in less than an hour.

Which stocks led the fall?

Samsung Electronics fell 4.59% in early trading to around 218,500 won, losing the 220,000-won level. SK hynix fell 5.1% to about 1,397,000 won, briefly dropping below 1,400,000 won and touching 1,394,000 won, down 5.3%.

The selling was broad. Hyundai Motor fell 1.57%, Doosan Enerbility dropped 3.77%, and HD Hyundai Heavy Industries fell 2.26%, according to Yonhap reporting. Among the ten largest KOSPI stocks, Samsung Biologics was a rare exception, rising more than 3%.

Foreign and institutional investors were the sellers. By around 9:30 a.m., foreign investors had sold a net 388.1 billion won of KOSPI shares and institutions a net 308.2 billion won, while retail investors bought a net 670.4 billion won — absorbing the selling, as they have through much of this volatile stretch.

Why is it blowing up?

The trigger came from Wall Street on Monday. The Nasdaq Composite fell 1.07% to 25,164.32 and the S&P 500 fell 0.51% to 7,541.40, while the Dow Jones Industrial Average rose 0.41% to 51,983.98. Chip stocks were hit hardest: the Philadelphia Semiconductor Index fell 3.37%, Intel dropped 8.83%, AMD fell 7.52%, and Micron fell about 5.8%.

Two U.S. moves fed directly into Seoul's open. Marvell fell more than 12% after its $115 billion deal for Lumentum, and Oracle fell about 8.8% after filing to raise $20 billion in stock and debt for its AI buildout. For investors in Samsung and SK hynix — the memory-chip suppliers at the heart of the AI data-center boom — those falls revived the same question that has driven the recent swings: is AI spending growing faster than the profits it will return?

Tuesday is also voting day in the U.S. midterm elections, adding a layer of political uncertainty. Safe-haven demand rose in Asia, and traders were reluctant to hold large chip positions into the result.

How did the rest of Asia trade?

South Korea dragged the region lower. The MSCI Asia Pacific gauge slipped 0.5%, and Taiwan's TAIEX lost 1.21% as its own chip shares followed the U.S. lead. Japanese markets were closed for the Culture Day national holiday, so there was no Nikkei session to cushion or confirm the move. Hang Seng futures, by contrast, rose 0.7%, and the Korean won strengthened 3.95 won to 1,342.05 per dollar — a sign this was a stock-specific risk selloff, not a broader currency crisis.

In India, GIFT Nifty pointed to a positive start — a reminder that Tuesday's pain was concentrated in AI-linked technology, not spread evenly across Asia.

What's next?

The next test comes from the United States. Voters decide the midterms on Tuesday, AMD reports earnings after the U.S. close, and U.S. job openings data lands the same day, ahead of Thursday's jobless claims and Friday's payrolls report. If U.S. chip stocks stabilise, Seoul's heavyweights have repeatedly shown they can rebound fast — Monday's V-shape is the recent proof. If the AI-spending doubts deepen, Samsung and SK hynix remain the first stocks global investors sell.

This report describes what happened and why markets reacted; it is not a recommendation to buy, sell, or hold any security.

Sources

Korea JoongAng Daily — Korean stocks plunge as AI spending fears rattle Samsung and SK hynix
Aju Press — KOSPI opens lower amid lingering AI woes ahead of US midterms
Business Today / Yonhap — Kospi Drops 3.36% At Open On AI Spending Concerns
TradingKey — Japan Markets Closed; South Korea's Kospi Drops Over 3%
Seoul Economic Daily — Samsung, SK hynix Slide on U.S. AI Selloff

FAQ

How much did the KOSPI fall on November 3?

It opened down 2.46% at 5,715.19 and fell as much as 3.59% to 5,649.03 in early trading, after closing Monday at 5,859.08.

Why did Samsung and SK hynix fall about 5%?

U.S. chip stocks slid overnight — the Philadelphia Semiconductor Index fell 3.37% — on renewed doubts about AI spending returns, and Seoul's chip giants moved in tandem.

Did retail investors buy the dip in Seoul?

Yes. By around 9:30 a.m., retail investors had bought a net 670.4 billion won of KOSPI shares, while foreign and institutional investors were net sellers.

Why was Japan's market not trading?

Japanese markets were closed on Tuesday, November 3 for the Culture Day national holiday, so there was no Nikkei session that day.