South Korea's KOSPI tumbled past four percent on July 20, 2026. Trading halted for twenty minutes after the plunge. Samsung and SK Hynix dragged the index lower. Sluggish demand for AI memory chips hit tech stocks hardest.
Exchanges then triggered a sell-side safety brake to slow the slide. Heavy bets on fast-rising AI shares amplified the decline. Memory chip shares sank more later as U.S. markets had already tumbled badly.