South Korea’s benchmark KOSPI index fell 7.1% on October 15, triggered by a sharp sell‑off in technology shares after hotter‑than‑expected US inflation data sparked AI‑related concerns. Samsung Electronics and SK Hynix led the decline, prompting a rare market‑stabilisation sidecar.
South Korea’s benchmark KOSPI index crashed 7.1% to 5,584.83 on Thursday, October 15, as a wave of technology‑stock selling intensified following hotter‑than‑expected US consumer‑price data (source [1]). The index opened 5.59% lower at 5,705.42, down 303.39 points (5.05%) by 9:11 a.m. local time, prompting the Korea Exchange to activate a sell‑side sidecar at 9:08 a.m. to pause program‑trading sell orders for five minutes (source [1]). A similar sidecar was triggered on the KOSDAQ at 9:12 a.m., marking the first dual activation in 51 trading days since July 29 (source [1]).
The market turmoil was sparked by US inflation accelerating to 3.7% in September, raising expectations of further Federal Reserve rate hikes (source [1]). The data sent the Nasdaq Composite down 1.9% and the S&P 500 off 1.1% overnight, while the US semiconductor index extended its losing streak to six sessions (source [1]). In South Korea, semiconductor giants bore the brunt: Samsung Electronics fell 8.2% and SK Hynix dropped 10.8% during the session (source [1]). Other AI‑linked firms also suffered steep losses, with Samsung Electro‑Mechanics sliding 15% and Hyosung Heavy Industries down 13% (source [1]).
A sidecar is a market‑stabilisation tool used by the Korea Exchange that temporarily suspends program‑trading sell orders when KOSPI 200 futures decline by at least 5% from the prior close and stay at that level for a minute (source [1]). The mechanism is intended to curb excessive volatility during sharp market moves.
Analysts cited by the Financial Times linked the broader tech sell‑off to concerns over inflation‑driven borrowing costs and the earnings outlook for AI‑focused companies (source [1]). With the sidecar now lifted, market participants will watch for further price action as investors reassess exposure to semiconductor and AI‑related stocks amid lingering macro‑economic uncertainty.