KOSPI

The KOSPI (Korea Composite Stock Price Index) is the primary benchmark index of the Korea Exchange (KRX), listing all common stocks on the market since its launch in 1980. Unlike price-weighted indices such as the Nikkei 225, the KOSPI is market-capitalisation weighted, giving larger companies proportionally greater influence. Samsung Electronics and SK Hynix are among its biggest constituents, making the index particularly sensitive to technology sector moves as well as macroeconomic shocks.

South Korea imports roughly 70% of its crude oil from the Gulf, making the KOSPI acutely sensitive to Strait of Hormuz disruptions. When the Iran-Israel-US conflict escalated in early March 2026, the KOSPI plunged 12% in a single session, its worst single-day loss on record; both Samsung Electronics and SK Hynix posted double-digit falls. Within the following two weeks the index fell a further 8%, triggering its second circuit breaker in four sessions, as Brent crude hit $119.50 per barrel intraday. The depth of the sell-off underscored that a conflict thousands of kilometres away can translate directly into record domestic losses for an energy-import-dependent economy.

The circuit breakers deployed in 2026 were a reminder that extreme volatility in a concentrated export economy can cascade through settlement systems and force regulatory intervention. The KOSPI's trajectory during the crisis also diverged sharply from the S&P 500, which recovered on de-escalation signals, highlighting the asymmetric exposure of Gulf-dependent Asian economies compared with the United States.