South Korea’s benchmark KOSPI index fell as much as 9% intraday on June 8, triggering circuit breakers and halting trading. The culprits: Samsung Electronics and SK Hynix, the same two chipmakers that had powered nearly all of the index’s gains this year.
Samsung Electronics dropped over 10% on the day, while SK Hynix declined by roughly 7-8% at various points during the session. The KOSPI ultimately closed down approximately 8.3%, landing at levels that wiped out weeks of accumulated gains in a single trading day.
A two-stock index meets gravity
Samsung Electronics and SK Hynix together accounted for up to 70% of the KOSPI’s gains during 2026. Both companies had briefly touched market valuations near $1 trillion, fueled by insatiable global demand for AI memory chips.
The sell-off didn’t materialize out of nowhere. It started building on June 5, when the KOSPI closed at 8,160.59, already down 5.5% after falling as much as 6.9% during the session. Foreign investors net-sold shares worth 3.5 trillion won that day alone, roughly $2.5 billion worth of Korean equities heading for the exits.
