South Korea’s KOSPI plunges 7.57% as AI doubts rattle investors

South Korea’s stock market just had the kind of day that makes portfolio apps feel like horror films. On October 15, 2026, the KOSPI index fell 7.57% to close at 5,554.22, its lowest finish since April. The culprit was a growing crisis of faith in artificial intelligence. Specifically, investors are asking whether the enormous sums being poured into AI infrastructure will ever turn a profit. A market built on chips meets a wall of doubt The damage was concentrated where you would expect. Samsung Electronics dropped about 9.5% on the day, while SK Hynix slid approximately 11%. And these were not one-off stumbles. SK Hynix now sits roughly 35% below its peak value, while Samsung is down roughly 22% from its high. The index itself has fared even worse. The KOSPI peaked at 9,386 in June 2026 and has since fallen approximately 40% from that level. The selling was severe enough to trigger circuit breaker interventions on multiple trading days, including October 15. Circuit breakers are automatic pauses that halt trading when prices fall too fast. What lit the fuse Several forces converged at once. First came higher-than-expected US inflation data. Hotter inflation raises the odds that in...