Korea’s main stock index fell 7.57% in one day. Memory chip makers led the drop.
On 15 October 2026 the KOSPI had one of its sharpest one-day falls, and the two biggest memory makers fell even more. Here is what happened, with the numbers and where they come from.
1. The day
The KOSPI opened 5.59% lower and closed down 7.57% at 5,554.22. A sell-side sidecar paused program selling at 9:07 a.m., and a market-wide circuit breaker halted trading for 20 minutes at 12:38 p.m. The KOSDAQ fell 7.65%. [1]
2. The week
From its 8 October close of 6,625.93 to 5,554.22 on 15 October, the KOSPI fell 16.2% over five trading days (9 October was a holiday). [2]
3. The chip makers
SK hynix fell 11.06% to 1,262,000 won and Samsung Electronics fell 9.48% to 210,000 won. [1] [2]
4. Who sold
Foreign investors sold a net 3.62 trillion won (about $2.68 billion). Individuals bought a net 1.29 trillion won and institutions 1.69 trillion won. [1]
5. Why, according to reports
Reports tied the fall to US consumer price data and worries that the Federal Reserve could raise interest rates further. [1] Higher rates make borrowing for AI build-outs more expensive; that link is our reading, not a reported cause.
6. The test
One day is a signal, not a verdict. What would change the picture: whether foreign selling slows, the next US rate signals, and the chip makers’ own results. This note is not advice to buy or sell anything.
Sources
- The Korea Herald, “Kospi slides over 7% as chip stocks sink,” 15 Oct 2026. koreaherald.com
- Daily closing prices, KOSPI index and SK hynix / Samsung Electronics shares (Korea Exchange data via Yahoo Finance), 8–15 Oct 2026. finance.yahoo.com
Image credits
- Cover and carousel slide 1: illustration made for YosQuant.