Summary
South Korea's main stock index fell sharply on Thursday, pushed down primarily by heavy losses in semiconductor stocks. The KOSPI declined 7.2% as investors pared positions in AI-linked chipmakers amid concerns over valuation levels and renewed geopolitical tensions. The Korea Exchange activated a sell-side sidecar earlier in the trading session after KOSPI 200 futures dropped more than 5% and stayed below that threshold for at least one minute.
Market moves and triggers
The exchange's sidecar measure halted program sell orders for five minutes, a step aimed at slowing automated selling pressure. That mechanism differs from a market-wide circuit breaker - which would be triggered if the KOSPI falls 8% or more from the previous close - because a sidecar pauses only program trading while a circuit breaker suspends all trading temporarily to allow market participants to digest information, reduce panic selling and restore orderly conditions during extreme volatility.
Where the selling was concentrated
Technology companies bore the brunt of the decline. Semiconductor leaders SK Hynix Inc (KS:000660) and Samsung Electronics Co Ltd (KS:005930) plunged 10.3% and 8.2% respectively, intensifying downward pressure on the index given their large weightings. The selloff was tied to continued investor unwinding of positions in AI-linked chipmakers amid worries about stretched valuations and geopolitical tensions.
Across the region, Japan-listed names tied to Apple's supply chain also saw steep declines. Kioxia Holdings Corp (TYO:285A) fell 13.4%, Murata Mfg Co (TYO:6981) dropped 4.4% and TDK Corp (TYO:6762) lost 3.2%, signaling broad weakness in the technology sector beyond South Korea's borders.
Implications
The combination of outsized declines in a few heavyweight semiconductor stocks and weakness in related supply-chain suppliers pushed the benchmark close to the threshold that would halt all trading. With the KOSPI down 7.2%, it approached the 8% decline level that prompts a full circuit breaker, a measure intended to cool extreme moves by pausing the market entirely.
Context limitations
The account here is limited to the movements and measures described above. Where information is limited, the article reflects only the stated facts: the percentage declines for the index and named securities, the activation and function of the sidecar, and the definition of the circuit breaker trigger.
Key figures cited
- KOSPI decline: 7.2%
- SK Hynix (KS:000660): -10.3%
- Samsung Electronics (KS:005930): -8.2%
- Kioxia Holdings (TYO:285A): -13.4%
- Murata Mfg (TYO:6981): -4.4%
- TDK Corp (TYO:6762): -3.2%