South Korea's benchmark stock index just had one of its wildest days on record. At the time of writing, MSN reported the KOSPI was up 18.27% at 6,615.60, putting it on track for its biggest single-day percentage gain ever. The Financial Times described the market as soaring 18% "as investors pile back into AI," while BNN Bloomberg tied the jump to a surge in chipmaking stocks. Outlook Business put the move at a record 17% — the exact figure varies by outlet and by the moment it was measured, but the direction is not in dispute.
The trigger, according to multiple reports, came from across the Pacific. Firstpost reported that strong cloud earnings from Microsoft and Amazon "reignite confidence in AI infrastructure spending," setting off a sharp rebound in semiconductor stocks across South Korea and Japan. Outlook Business similarly credited strong Microsoft earnings with reviving confidence in AI spending.
Korea's two memory-chip giants did the heavy lifting. Firstpost reported SK Hynix up 25% and Samsung up more than 20%; a separate MSN report put the gains at 28% and 24% respectively.
The rally follows a rough stretch. CNBC characterized the Korean market as "bipolar," citing meltdowns alongside the record rally, and Business Insider called it one of the wildest months in the market's history. The Motley Fool, writing about AI names more broadly, framed the moment as a bounce back "after the bloodbath."
Why it matters: South Korea makes the memory chips that AI data centers run on, so a single day's swing there is a real-time referendum on whether the world's biggest tech companies will keep spending on AI — and how violently markets now react when that answer changes.