Why Is KOSPI Crashing? What Is Shaking Korea’s AI Rally?

South Korea’s KOSPI closed at 6,035.35 on October 13, down 5.46%, after falling more than 7% during the session. Across five consecutive declining trading sessions, the index has lost 13.83%. A market celebrated for its spectacular rally is now confronting a difficult question: how much of that rally depended on exceptionally profitable conditions for a small number of memory-chip companies?

The immediate shock came from Chinese chipmaker ChangXin Memory Technologies, or CXMT, outlining plans for a new server-memory product. That added to concerns about the financing of future AI investment, while foreign investors sold roughly 4.5 trillion won of KOSPI shares on October 13. Samsung Electronics and SK hynix led the decline, finishing down 7.39% and 10.09%, respectively.

The deeper issue is the durability of profits. Korea’s chipmakers are still reporting strong earnings, but investors are questioning how long memory shortages, high prices and rapid AI spending can support them. Understanding that distinction explains why the KOSPI can fall sharply even when the companies behind its earlier rise remain profitable.

How Much Has KOSPI Fallen in October 2026?

The latest fall is part of a sequence of losses. The five declining sessions were October 6, 7, 8, 12 and 13, with the index closing progressively lower each day.

Source: Investing.com historical closing prices. Cumulative decline: INDmoney calculation using the October 2 and October 13 closes. Daily percentages are rounded.

The closing-price calculation is: (6,035.35 ÷ 7,003.74 − 1) × 100 = -13.83%.

The longer perspective is equally revealing. KOSPI rose 75.6% in 2025 and ended that year at 4,214.17. At the October 13 close, it remained 43.22% above that level, while sitting 35.70% below its June record of 9,385.59. These are price-index comparisons in Korean won, excluding dividends.

Both statements can be true: an investor who entered much earlier may still have substantial gains, while someone who entered near the peak may have suffered a large loss. A market’s annual performance tells you little about the experience of an investor arriving at a different point in the rally.

Why Is KOSPI Falling Today? Four Forces Behind the Sell-Off

1. China’s CXMT Is Challenging Expectations About Memory-Chip Profits

On October 10, CXMT president Cao Kanyu outlined a new DRAM architecture called 4F² and said the company expected to introduce DDR5 server-memory modules using it by the end of 2026, according to Yicai’s reporting from the industry conference. The design aims to fit memory cells into less space, potentially improving how much data a chip can store.

For investors, the important question is how additional competition could affect selling prices. Memory manufacturers have benefited from strong demand and limited supply. If another producer can supply competitive products in meaningful quantities, customers could gain more negotiating power and existing suppliers could face pressure on margins.

Think of a supplier charging high prices because a product is difficult to obtain. A credible new supplier can change expectations about those prices before its products arrive in large volumes. Stock markets respond to that possible future change, even while the established supplier’s current business remains strong.

However, the product distinctions matter. DDR5 server memory and high-bandwidth memory, or HBM, serve different roles. HBM is stacked memory designed to feed data rapidly to powerful processors, including AI accelerators. A proposed DDR5 product does not establish that CXMT has matched Samsung or SK hynix across their most advanced AI-memory products.

The commercial test also comes later: manufacturing at scale, producing chips reliably and meeting customers’ requirements. CXMT’s announcement raises a competitive risk; it does not, by itself, prove that Korean chipmakers have already lost their technological lead or that their earnings have deteriorated.

2. AI Spending Faces a Financing Question

At the DBS Asia Future Forward Conference on October 12, Broadcom CEO Hock Tan warned that access to capital could become a bigger constraint on AI expansion than shortages of chips or electricity. Intel CEO Lip-Bu Tan also highlighted financing costs and the need to demonstrate investment returns. Both executives remained positive about near-term demand, according to Investor’s Business Daily.

That warning matters to Korea because memory orders depend partly on customers’ willingness and ability to keep building AI infrastructure. A data-centre project needs money for processors, memory, power and buildings well before it generates its eventual return. Higher financing costs or weaker expected returns can make the next project harder to justify.

The connection to chip profits is straightforward. If customers slow the pace of expansion, suppliers may face slower order growth. If competing supply increases at the same time, the market could move away from the shortages that supported unusually high selling prices.

AI adoption can continue growing under that scenario. What changes is the pace of infrastructure spending and how much profit suppliers retain from each additional sale. Investors need to distinguish the long-term usefulness of AI from the earnings expectations embedded in AI-related shares.

3. Foreign Selling Has Added Sustained Pressure

Foreign investors’ roughly 4.5 trillion won of net selling on October 13 followed substantial earlier reductions in exposure. Seoul Economic Daily, citing Korea Exchange data, reported 21.51 trillion won of foreign net selling in KOSPI shares during September. Samsung Electronics and SK hynix accounted for 76.6% of that September total.

The figures support the concern that overseas investors are reducing exposure to important parts of Korea’s equity market. They also show why the selling is so influential: it is concentrated in the same large companies that helped power the earlier rally.

Net selling measures shares sold minus shares purchased over a period. It does not show where the proceeds ultimately went, and it does not mean foreign investors have abandoned every Korean company or withdrawn from all Korean assets. It is evidence of reduced demand for these shares at the prevailing prices.

Several motivations can overlap. Investors may question future profits, take gains after a strong rally or reduce a portfolio’s concentration in semiconductors. Rising US bond yields also increase the return available from an alternative asset, raising the return investors may demand from equities. September reporting identified that rate backdrop as one contributor to the selling.

Currency movements add another consideration for international investors. A weaker won can reduce returns measured in dollars, although the effect on individual exporters’ earnings is more complicated.

4. Samsung and SK Hynix Make the Index Especially Sensitive

KOSPI is South Korea’s main stock-market benchmark. Larger companies have greater influence over its movement, so a sharp fall in a few very large constituents can pull down the national index even when the damage across other businesses is smaller.

The Financial Times reported on October 13 that Samsung Electronics and SK hynix together account for about half of the benchmark. That makes concerns about the memory industry unusually powerful for KOSPI.

For illustration, if companies representing 50% of an index fall 9% and all other constituents are unchanged, the index would fall approximately 4.5%. This simplified example is not an attribution of October 13’s exact decline, but it shows why two companies can have such a large effect.

Concentration also worked in the opposite direction during the rally. Investors who benefited from the rising index were receiving substantial exposure to a shared driver: the outlook for memory-chip profits. A country index can contain many companies while still depending heavily on one industry.

Why Are Samsung and SK Hynix Falling Despite Strong Earnings?

Current earnings provide an important counterweight to the fears. Samsung’s October 8 guidance projected approximately 195 trillion won of third-quarter revenue and 107.4 trillion won of operating profit. SK hynix’s second-quarter release reported 79.32 trillion won of revenue and 60.54 trillion won of operating profit.

Sources: Samsung Global Newsroom, October 8, 2026; SK hynix Newsroom, July 29, 2026. Figures are consolidated and rounded. Samsung’s row is guidance; the SK hynix release also identifies its figures as preliminary and subject to review. The periods differ.

These figures show that the sell-off is occurring alongside strong reported operating performance. They do not establish how much profit either company will earn next year. Share prices can fall when investors become less confident about future earnings, even if the latest quarter is impressive.

Memory chips are particularly exposed to this. Shortages can lift prices and profits sharply, encouraging manufacturers to add capacity. When supply catches up, customers can regain bargaining power. The relevant question is how much of today’s profit reflects a lasting advantage and how much reflects unusually favourable supply conditions.

There is evidence supporting the stronger business case, too. In its Q2 release, SK hynix said it had secured long-term agreements with around ten customers and begun mass shipments of HBM4 during the quarter. Those developments support a view that customer relationships and advanced products can make some demand more durable, although they do not eliminate pricing or investment risk.

Our assessment is that the current sell-off reflects a reassessment of future profitability and investor willingness to own these shares. Strong current results argue against assuming the entire business case has collapsed. The competitive and financing concerns argue against assuming those results can continue indefinitely.

Is KOSPI Cheap After the Crash? Why Earnings Matter

A large price decline makes a market cheaper relative to its earlier price. Whether it offers better value depends on the earnings investors can reasonably expect in future years.

Consider a hypothetical company whose shares cost 100 currency units and whose annual earnings per share are 10. Its price-to-earnings ratio, or P/E, is 10 times: investors pay ten units of share price for each unit of annual profit.

Source: INDmoney illustration. All inputs are hypothetical and are not actual KOSPI or constituent valuations. P/E equals share price divided by annual earnings per share.

The third row explains the trap. The share price is lower, but it costs more per unit of profit because earnings fell faster. In a cyclical industry, using an exceptionally profitable quarter as the basis for a long-term valuation can make a stock appear more attractive than it is.

For Korean equities, a useful valuation assessment tests what happens if memory prices become less favourable, competitors gain ground or customers slow investment. A fall from the peak provides context, but it cannot establish fair value without an earnings assumption. The same caution applies to a recovery target based only on the index returning to its previous high.

What Would Support a KOSPI Recovery?

A temporary rebound and a durable recovery can have different causes. A sharp bounce may follow a period of intense selling; a more convincing recovery would combine firmer demand for shares with better evidence about future profits.

The following signals would help assess that distinction:

• Memory prices and profitability: Are chip prices remaining firm as supply expands? Revenue growth would be more reassuring if margins and cash generation also remain strong.
• Customer spending and orders: Are major AI customers maintaining investment plans and translating them into funded orders? Announced ambitions need to be assessed alongside financing and delivery schedules.
• CXMT’s commercial progress: Does the proposed product reach customers at scale, with reliable performance and competitive costs? A launch target and a meaningful change in industry supply are different milestones.
• Foreign flows and market breadth: Does overseas demand improve over several sessions, and does the recovery extend beyond the two largest chipmakers? A broader improvement would reduce the index’s dependence on a narrow rebound.
• Earnings expectations: Do forecasts stabilise as companies explain their pricing, product mix and investment plans? A rising index accompanied by falling profit forecasts would require closer scrutiny.

There was also a trading curb during October 13’s session. Reporting from the exchange described a five-minute suspension of programme sell orders, known as a sidecar. This curb addresses rapid trading pressure; it does not resolve the underlying questions about competition or earnings.

Earlier episodes of volatility are covered in INDmoney’s analysis of Korea’s chip stocks and leveraged ETFs. For the current decline, the useful recovery test is whether the business outlook and demand for shares improve together.

What Does the KOSPI Crash Mean for Indian Investors?

For an Indian investor, Korean equities can provide access to companies and industries that are less represented in the domestic market. However, geographical diversification does not automatically mean diversification across different sources of risk.

A portfolio already exposed to NVIDIA, semiconductor funds or AI infrastructure stocks may have significant dependence on the same spending cycle that supports Korean chipmakers. Adding a Korean fund changes the country and companies involved, but can increase exposure to a familiar investment theme.

The vehicle matters as well. The iShares MSCI South Korea ETF, EWY, follows the MSCI Korea 25/50 Index, according to BlackRock. It provides Korean equity exposure through a US listing, but its benchmark, constituent weights and returns differ from KOSPI’s.

Before adding exposure, examine the fund’s largest holdings, concentration, fees and overlap with existing investments. Korean share prices, the won’s movement against the dollar and the rupee’s movement against the dollar all affect the eventual rupee result. Trading an ETF in dollars does not remove the currency exposure of its underlying Korean assets.

INDmoney’s South Korea ETFs page provides a starting point for comparing available funds. The investment case should rest on the exposure sought, a realistic view of future earnings and the size of the allocation within the overall portfolio.

What the KOSPI Sell-Off Is Telling Investors

The KOSPI crash brings together a fresh competitive threat, concern about funding future AI spending and substantial foreign selling. Heavy concentration in Samsung and SK hynix turns those pressures into a large move in the benchmark.

Our view is that record profits provide a reason to examine the underlying businesses carefully, while their dependence on favourable memory-market conditions calls for realistic earnings assumptions. A sharp index decline alone cannot establish either that Korea’s opportunity has disappeared or that the market now offers attractive value.

The most useful question is how much profit Korean chipmakers can sustain when supply becomes more competitive and customers become more selective about spending. Evidence on that question will matter more than the size of a single rebound.