KOSPI weekly October 12-16, 2026: down 14.46% to 5,668.05 — why it fell four days straight, and who came back Friday
The KOSPI index of South Korea fell 957.88 points, or 14.46%, in the week of October 12-16, 2026, from 6,625.93 to 5,668.05. It lost 3.65% on Monday, 5.46% on Tuesday, 0.44% on Wednesday and 7.57% on Thursday, when a circuit breaker halted trading, before rising 2.05% on Friday. Doubts about AI revenue and debt, a 3.7% US inflation reading and Chinese memory competition hit at once, and foreign investors led the selling. On Friday they turned net buyers for the first time in nine sessions
The three lines
- Numbers — 6,625.93 to 5,668.05, down 957.88 points (14.46%), circuit breaker on Oct 15
- Causes — AI revenue and debt doubts, 3.7% US CPI, Chinese memory catch-up, all in one week
- Friday — foreigners net buyers after eight selling days; KOSDAQ up 4.46%
Key questions
- KOSPI weekly performance October 12-16 2026
- **Down 14.46% for the week.** | Date | Close | Change | |---|---|---| | Oct 8 (prior session) | 6,625.93 | — | | Oct 12 (Mon) | 6,384.24 | -3.65% | | Oct 13 (Tue) | 6,035.35 | -5.46% | | Oct 14 (Wed) | 6,008.81 | -0.44% | | Oct 15 (Thu) | 5,554.22 | -7.57% | | Oct 16 (Fri) | 5,668.05 | +2.05% |
- KOSPI close October 16 2026
- **KOSPI closed at 5,668.05 on October 16, 2026, up 113.83 points (2.05%).** | Item | Oct 16 | |---|---| | Intraday high | 5,809.94 | | Intraday low | 5,590.33 | | KOSDAQ | 794.78 (+4.46%) | | Won per dollar | 1,331.4 (-13.2) | | Foreign investors | Net buyers (about 341-352 billion won) |
- Why did Korean stocks fall in October 2026
- **Three shocks converged on Korea's two chip giants.** | Cause | Number | |---|---| | AI revenue and debt doubts | CoreWeave bond yields near 15%; Anthropic growth slowed to 45% | | US rate-hike fears | September CPI 3.7% vs 3.6% expected | | Chinese memory | CXMT 4F2 DRAM progress | | Foreign selling | About 2.02T won (Oct 12), 4.51T won (Oct 13), 3.6T won (Oct 15) |
Korea's benchmark lost more than a seventh of its value in five trading days. The KOSPI fell from 6,625.93 (the October 8 close, the last session before the Hangeul Day holiday on October 9) to 5,668.05 over October 12-16, 2026 — down 957.88 points, or 14.46%. It fell on four of five days, and on Thursday it dropped more than 8% intraday, triggering a market-wide circuit breaker. Friday's 2.05% gain was the week's only up day.
For international readers: the KOSPI is unusually concentrated. Samsung Electronics and SK hynix, the world's top memory-chip makers and key suppliers of high-bandwidth memory (HBM) for Nvidia's AI accelerators, make up a large share of its market value. When investors question AI spending, Seoul often moves more than New York.
1. Day by day
| Date | Close | Change | Main driver |
|---|---|---|---|
| Oct 8 (Thu, prior) | 6,625.93 | -2.62% | Profit-taking after Samsung's preliminary Q3 earnings |
| Oct 12 (Mon) | 6,384.24 | -241.69 (-3.65%) | OpenAI revenue questions and US AI-stock weakness over the holiday; foreigners sold about 2.02T won |
| Oct 13 (Tue) | 6,035.35 | -348.89 (-5.46%) | China's CXMT memory announcement; foreigners sold about 4.51T won; intraday low 5,911.11 |
| Oct 14 (Wed) | 6,008.81 | -26.54 (-0.44%) | Waiting for US inflation data |
| Oct 15 (Thu) | 5,554.22 | -454.59 (-7.57%) | US CPI at 3.7%; CoreWeave bond rout; circuit breaker |
| Oct 16 (Fri) | 5,668.05 | +113.83 (+2.05%) | Bargain buying; foreigners net buyers for the first time in nine sessions |
The small-cap KOSDAQ followed the same path, starting the week at 849.19 (-4.83%) and ending Friday at 794.78 after a 4.46% rebound that briefly triggered a buy-side "sidecar" curb on program trading around 12:55 p.m.
2. Why it fell — three shocks in one week
| Cause | When it surfaced | Key figure | How it reached Korea |
|---|---|---|---|
| AI revenue and debt doubts | Holiday through Oct 15 | Disputed OpenAI revenue math; CoreWeave bonds near 15% yield; Anthropic growth slowing to 45% | Questions over AI capex → weaker HBM and memory outlook |
| US rate-hike fears | Night of Oct 14 (Korea time) | September CPI 3.7% vs 3.6% expected; core 2.6% | Higher discount rates for growth stocks; selling of won assets |
| Chinese memory catch-up | Around Oct 13 | CXMT 4F² DRAM progress | Market-share and price worries for Samsung, SK hynix |
All three converge on the two chip giants. On Thursday alone Samsung Electronics fell 9.48% and SK hynix 11.06%. CNBC estimated that 20 of the world's most valuable AI and semiconductor stocks lost more than $1 trillion in market value over the week.
Foreign investors drove the selling, net sellers for eight straight sessions through October 15, with that day's outflow of about 3.6 trillion won reported as a record. Domestic retail investors absorbed most of it.
3. Was Friday a turn?
| Indicator | Oct 16 | Reading |
|---|---|---|
| KOSPI intraday high | 5,809.94 | Gains partly given back in the afternoon |
| Foreign investors | Net buyers, roughly 340-350 billion won | First net buying in nine sessions |
| Samsung Electronics | +2.62% to 215,500 won | Seen as oversold |
| SK hynix | +0.79% to 1,272,000 won | Small bounce |
| Won per dollar | 1,331.4 (-13.2) | Exporter dollar selling |
Local analysts called it a technical rebound. Closing well below the intraday high, and SK hynix gaining less than 1%, suggest buyers are not yet confident.
4. What to watch next week, and what is unconfirmed
- October 22: Bank of Korea monetary policy meeting — the first rate decision after the crash.
- October 27-28: US Federal Reserve meeting, after the inflation surprise.
- Anthropic IPO pricing: Reports that investors now discuss a $1.5 trillion valuation, down from $2 trillion, feed into how AI assets are priced.
- Unconfirmed: Foreign flows for October 14, and final investor-flow data for October 16, should be checked against Korea Exchange figures.
Sources
- Asia Economy — KOSPI closes at 6,384.24, down 3.65% (Oct 12)
- Seoul Shinmun — KOSPI closes at 6,035.35, down 5.46% on heavy foreign selling (Oct 13)
- Newspim — KOSPI, KOSDAQ close lower (Oct 14)
- BusinessKorea — KOSPI plunges 7.57% to the 5,500 level on foreign selling (Oct 15)
- BusinessKorea — KOSPI ends seven-session losing streak, back above 5,600 (Oct 16)
- Money Today — KOSPI closes up 113.83 points (2.05%) at 5,668.05