Why the world's top-performing stock market in 2025 is seeing historic volatility

TOPSHOT - Currency dealers monitor exchange rates in a foreign exchange dealing room at the Hana Bank headquarters in Seoul on February 2, 2026. South Korea’s benchmark index Kospi tumbled more than five percent on February 2, in line with a sell-off across Asian markets amid fresh worries about an AI-fuelled tech rally that has sparked fears of a bubble in the sector. (Photo by Jung Yeon-je / AFP via Getty Images)

Jung Yeon-je | Afp | Getty Images

South Korea’s stock market has swung wildly in recent days, underscoring how the world’s best-performing equities market last year is turning into its most volatile one.

The benchmark Kospi index plunged as much as 12% on Wednesday, marking its largest single-day drop on record, before staging a powerful rebound in the next session, up nearly 10%, marking its best day since 2008. It was trading over 1% lower on Friday.

The whipsaw comes as investors reassess risks from the escalating war in the Middle East, which has sent oil prices surging and rattled markets globally, and the market’s concentration in a few stocks.

While the global risk-off mood has played a major role, experts said Korean market’s concentration in two memory giants and its sensitivity to energy shocks has made it particularly vulnerable to sharp swings.

“Korea is a bit of an outlier, if you look at the other stock markets’ reaction,” said Jason Hsu, chief executive officer at Rayliant Global Advisors. He added that the Kospi’s heavy concentration in a handful of technology stocks, meant that market moves tend to be magnified relative to more diversified indices.

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Performance of South Korean stocks year-on-year

“It is natural its volatility is enormous,” he told CNBC.

SK Hynix, is up nearly 45% this year, having skyrocketed 274% last year. Similarly, Samsung Electronics, which is up about 60% since the start of the year, surged 125% in 2025.

Both make up about one-third of Kospi’s total market capitalization as of early November, according to a report from the Korea Capital Market Institute.

That concentration tends to amplify volatility: when the memory chip cycle is strong the index can rally rapidly, but when investors take profits or sentiment turns risk-off, declines in those few heavyweight stocks can drag the entire market lower, said analysts.

The Kospi Volatility Index surged 27% to hit a record high on Wednesday at the height of the sell-off. It has since dipped to around 8% on Thursday, but remains at record high levels.

Retail leverage amplifies swings

Another factor amplifying the market’s moves is South Korea’s large base of retail investors and its active derivatives market, according to market veterans.

“This is just too much of the leverage trading that’s affecting the market,” said Daniel Yoo, global strategist at Yuanta Securities.

“We had a huge amount of margin calls for retail investors. So they just dumped it… And then [on Thursday] it went back up again. It has nothing to do with fundamentals.”

Retail investors have been among the biggest buyers of Korean stocks since the start of the year, often using margin accounts and via leveraged exchange-traded funds. That means sharp market drops can quickly trigger forced selling as margin calls hit, said Yoo.

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Individual investors were the biggest participants in South Korea’s stock market on Thursday, according to data from the Korea Exchange.

Individual traders sold 19.7 trillion won ($13.3 billion) worth of Kospi stocks and bought about 21 trillion won, making them the largest buyers on the market and leaving them with net purchases of roughly 1.3 trillion won.

Individual investors accounted for the largest share of trading on the Kospi on Thursday, making up about 45% of total turnover, compared with roughly 33% for foreign investors and 22% for institutions, according to Korea Exchange data on Thursday.

Adding to the turbulence is Korea’s sensitivity to energy prices. As a large importer of crude oil, the country is particularly vulnerable to disruptions in global supply.

“While we had seen sell-offs in major equity markets driven by the uncertainties around the Middle East, it has been more pronounced in South Korea [on Tuesday and Wednesday] given its relatively higher dependence on crude oil imports,” said JPMorgan Asset Management’s global market strategist Raisah Rasid.

Semiconductor cycle still supportive

For now, the market’s choppiness may simply reflect the unwinding of an overheated rally, said  KB Securities’ Kim.

“Given the scale of leveraged position of Korean retail investors and the expected prolonged uncertainty from the Iran situation, it would be premature to call for an immediate V-shaped recovery,” he added.

But with semiconductor earnings still strong and valuations stabilizing, other market watchers believe the underlying fundamentals of South Korea’s equity market remain intact, particularly in the semiconductor sector that dominates the index.

“The pullback appears to be knee-jerk and more sentiment-driven at this stage, rather than fundamentally driven,” said Kieron Poon, investment director of Asian equities at Aberdeen Investments.

Memory prices, particularly for Dynamic Random Access Memory (DRAM), have been rising after a strong 2025 and are expected to continue growing through the first half of 2026, supporting earnings for Korean chipmakers, he said.

JPMorgan’s Rasid echoed that view, saying the long-term drivers for Korean equities remain strong.

“While there are concerns around demand destruction and inventory hoarding, demand-supply dynamics in the memory chips space is likely to remain tight through this year and possibly the next,” she said.

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