South Korea's KOSPI Tumbles 10% as AI-Fueled Chip Rally Unravels

South Korea's benchmark KOSPI fell nearly 10% on June 23, triggering circuit breakers, as SK Hynix and Samsung Electronics each dropped over 12%. The sell-off highlights concentration risk in an index where two chip giants account for roughly half of total market value.

2026-06-25T05:19:27.281Z

South Korea’s KOSPI index plunged 9.99% on June 23, closing at 8,204 points, its steepest single-day drop in more than three months. The slide was severe enough to trigger circuit breakers, halting trading for 20 minutes.

SK Hynix and Samsung Electronics each lost more than 12% on the day. Together they represent nearly half of the KOSPI’s market capitalization, so their declines dragged the entire market down.

The sell-off follows a breathtaking rally. By June 2026, the KOSPI had doubled year-to-date, surging past 9,000 points on insatiable demand for high-bandwidth memory used in AI data centers. The Kospi 200 Volatility Index, a fear gauge, spiked to around 75 - four times its normal reading near 20.

Investors are now questioning whether AI-driven spending can justify such stretched valuations. South Korean regulators are also tightening rules on leveraged products, which could drain speculative capital that amplified the index’s climb. For investors, the concentration risk is unmistakable: when two stocks dictate roughly half the index, any wobble in memory chip demand becomes a market-wide shock.