South Korea's Stock Market Had Its Biggest Day Ever. Small Investors Sold.

South Korea's main stock index jumped 18% on July 31, 2026 — its largest one-day gain ever — led by Samsung's 27% surge and SK Hynix's 30% leap, fueled by strong US tech earnings. Yet everyday investors sold a record 10.5 trillion won worth of shares, while big institutions and foreign buyers snapped them up.