South Korea's benchmark index triggered a circuit breaker as foreign investors dumped $2.6 billion in shares during a broad tech selloff
South Korea’s stock market just had its worst day in recent memory. The KOSPI index cratered more than 8% on June 23, hitting a low of roughly 9.1% intraday, severe enough to trigger a Level 1 circuit breaker that halted trading for 20 minutes.
The culprits were familiar names. Samsung Electronics dropped more than 10%, while SK Hynix, which had just overtaken Samsung as Korea’s most valuable company earlier in the week, fell over 12%.
What triggered the selloff #
The proximate cause traces back to Broadcom’s earnings report from earlier in June. On paper, the numbers looked strong. Broadcom posted Q2 AI chip revenue of $10.8 billion, representing 143% year-over-year growth. But Broadcom slightly missed overall revenue estimates and kept its 2027 AI forecast unchanged. In a market that had been pricing in perpetual acceleration, “steady” reads as “disappointing.”
The result was a cascading selloff that started in US tech stocks and rippled across the Pacific. Foreign investors sold more than 4 trillion won, approximately $2.6 billion, worth of KOSPI shares during the downturn. Domestic retail investors stepped in to provide some floor, but the selling pressure was overwhelming.
The AI rally that set the stage #
The KOSPI had been on a remarkable tear, surging past record highs above 9,000. The rally was built almost entirely on semiconductor demand tied to AI infrastructure spending.
SK Hynix had been the poster child of this trade. The company makes high-bandwidth memory chips, the kind that AI data centers consume voraciously. Its ascent to Korea’s most valuable company, leapfrogging Samsung, was a testament to just how much money was flowing into AI hardware bets.
Margin debt across the Korean market had reached a record 38.5 trillion won earlier in June.
What this means for investors #
South Korea’s semiconductor sector sits at the heart of the AI supply chain. Samsung and SK Hynix together dominate global memory chip production. When their stocks fall double digits in a single session, it signals something broader: the market is questioning whether AI hardware demand can sustain the growth rates that current valuations require.
The $2.6 billion foreign selloff is particularly worth watching. Institutional investors don’t dump that volume on a whim. It suggests a meaningful reassessment of risk-reward in AI-adjacent equities.
Markets did show signs of a rebound in chip stocks following the initial panic, and the fundamental demand picture for AI hardware hasn’t fundamentally changed.
Micron’s upcoming earnings loom as the next catalyst. Another miss, or even guidance that fails to exceed expectations, could reignite selling pressure across the semiconductor complex. Investors navigating this space should be watching not just revenue numbers but inventory levels, order backlogs, and any signals about the pace of data center buildouts.
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