In seven trading sessions through Thursday, the KOSPI shed about a fifth of its value. The final session alone delivered a 7.57 percent rout. A rebound may soothe investors, but it should not lull policymakers into believing the storm has passed.
Markets may be imperfect weather vanes, but Korea can ill afford to ignore the direction in which the wind is blowing.
The temptation is to point to crowded order books and record earnings as proof that the market has lost its bearings.
But factories report what customers are buying now. Markets are trying to judge what those customers can afford next.
The latter matters for a country drawing almost half its export revenue from semiconductors. Korea’s industrial prowess is its own. The financial conditions sustaining its customers’ spending are not.
This week’s collision of American inflation, AI borrowing costs and Korean share prices has made that dependence painfully clear.
The foreign retreat predates this week’s panic. Foreign net selling of KOSPI shares reached 238.9 trillion won ($178 billion) this year through Thursday, against 9 trillion won in all of 2025, according to the Financial Supervisory Service. Thursday alone accounted for 4.87 trillion won. Whatever the mix of motives, the scale is difficult to dismiss.
Semiconductors generated $60.3 billion of Korea’s $120.94 billion in exports in September, almost half the total. The achievement is remarkable. So is the concentration of risk.
Its share cannot be confused with half the economy. Nevertheless, the industry’s influence reaches far beyond its factories. Chip profits sustain investment, supplier orders, bonuses and tax receipts. Export dollars help support the won. Share prices shape household wealth and confidence.
Several sources of economic resilience now draw strength from the same business cycle. They could also weaken together.
This week’s selloff brought that vulnerability into focus through an apparently distant catalyst: American consumer prices. U.S. inflation reached 3.7 percent in September from a year earlier, with prices rising 0.6 percent from August.
The figures reinforced concern that borrowing costs would remain elevated, subjecting the AI investment boom to a more demanding financial test.
The transmission to Korean chipmakers is straightforward. AI infrastructure requires enormous expenditure long before its ultimate returns are known. Data centers must be built, power secured and costly processors and memory installed.
For businesses borrowing heavily to expand, access to finance can be as consequential as demand for their services.
Higher rates raise the cost of that expansion while reducing the value investors place on future earnings. They also make safer assets more attractive relative to shares priced for years of rapid growth. Technological progress can continue even as the financial assumptions underpinning it unravel.
CoreWeave, the heavily indebted provider of AI computing capacity, illustrates the problem. Pressure on its bonds this week reflected concern about its ability to finance expansion on acceptable terms. Growing demand for AI does not, by itself, resolve that concern. Customers must generate revenue, lenders must be repaid and investment must eventually earn a return.
Samsung Electronics and SK hynix have very different financial profiles. Still, their strength cannot insulate them entirely from the financing constraints of businesses further along the AI supply chain. When money becomes more expensive or harder to obtain, projects can be postponed and orders scaled back. A credit problem abroad can become an earnings problem in Korea.
The movement in U.S. government bonds adds a subtler warning. Treasury yields initially rose after the inflation release, then fell as anxiety over AI investment drew money toward safety.
There is no contradiction. Corporate borrowing costs include a premium for the risk of nonpayment. That premium can widen even as government bond yields fall. Money can become cheaper for the U.S. Treasury while becoming more expensive for the businesses expected to sustain the next wave of chip orders. Korea needs to watch that gap as closely as it watches the Federal Reserve.
This does not establish that the AI boom is ending. Foreign selling can reflect redemptions, portfolio limits or a need to raise cash as well as doubts about future earnings. Even strong businesses can be caught in an indiscriminate retreat.
Record profits, however, offer no guarantee that a falling share price is a mistake. A stock can look inexpensive against exceptional earnings precisely when investors are questioning their durability. The next change in profits matters more to valuations than the last record quarter.
An abrupt collapse in AI demand is therefore not the only risk. A slowdown from an extraordinary pace of investment, greater competition or an easing of scarcity prices could produce a painful adjustment even as the technology continues to advance.
For Korea, the consequences could spread well beyond the stock exchange. Slower chip receipts could diminish the supply of export dollars just as foreign investors seek to move money out. A weaker won would raise import costs, complicating the Bank of Korea’s response to softer growth. Lower corporate profits could restrain investment and tax revenue, while stock-market losses could weigh on consumption, particularly among households that borrowed to join the rally.
The concern is how these pressures might reinforce one another.
For now, the buffers remain substantial. Even after Thursday’s plunge, the KOSPI stood 31.8 percent above its level at the end of last year. The won traded at 1,344.6 per dollar, stronger than 1,439.0 at year-end. Such resilience gives Korea room to prepare. It should not become an excuse for complacency.
Preparation starts with testing the assumptions prosperity has made comfortable. How would public finances withstand a normalization of semiconductor profits? How exposed are financial institutions to simultaneous losses in chip shares and AI-related credit? How much household borrowing rests on the belief that every market decline will quickly reverse?
Authorities should examine those exposures while earnings and export receipts still provide a cushion. Budgets should distinguish temporary windfalls from dependable revenue. Financial supervision should trace leverage and concentrated risks across institutions, including investments whose AI credentials may have discouraged closer scrutiny.
Industrial policy must also look beyond the next semiconductor capacity expansion. Preserving Korea’s technological lead is essential, but so is spreading productivity gains across smaller manufacturers and service businesses and allowing new sources of growth to emerge. A broader economic base would make the country better able to withstand a turn in the chip cycle.
Markets can exaggerate danger as readily as opportunity. Yet waiting for a warning to appear in factory orders, tax receipts and employment would defeat the purpose of heeding it.
Korea has earned its position at the center of the AI economy. This week’s rout reveals how much national prosperity now rests on that position — and on financial conditions beyond the country’s control.
The chip windfall has bought Korea time to strengthen the rest of its economy. The KOSPI’s warning is that it should use it.
*The author is the managing editor of AJP.
Copyright ⓒ Aju Press All rights reserved.