On October 12, the Korea Composite Stock Price Index (KOSPI) extended losses to 3%, closing at 6,427.08 points, with SK Hynix falling over 4% and Samsung Electronics dropping more than 3%.

This marks the latest chapter in months of relentless declines for South Korean stocks. Less than four months ago, the KOSPI stood at a historic peak of 9,385 points, hailed by global investors as the 'best representation of AI trading.'

Today, market turnover has collapsed by 70% from its May peak, with foreign capital outflows reaching $131 billion year-to-date. Samsung Electronics' foreign ownership ratio has fallen to its lowest level since the 2008 financial crisis.

From the 'world's best-performing stock market' to the 'world's worst-performing index,' South Korea's stock market has undergone a staggering role reversal in just one quarter.

This collapse is not driven by a single factor but by the convergence of multiple forces: the shift of the global AI narrative from frenzy to rationality, South Korea's deformity (Note: ' deformity ' is translated as 'overreliance' in context) dependence on memory chips, leveraged ETF-triggered retail investor panic, and systematic foreign capital withdrawal amid currency and interest rate pressures.

How the AI Narrative Elevated South Korean Stocks to Divine Status

To understand the intensity of this collapse, one must revisit the frenzy of its preceding rally.

In the first half of 2026, the South Korean stock market rewrote history at a dizzying pace. The KOSPI surged from around 4,200 points at the start of the year to hit 9,385.59 points on June 19, with a six-month cumulative gain exceeding 100%. Total market capitalization swelled to approximately $4.59 trillion, surpassing the UK and Canada to become the world's seventh-largest stock market.

The core driver of this rally was the AI-fueled 'super cycle' in memory chips. Goldman Sachs, in a May research report, labeled South Korean stocks as Asia's 'highest conviction' play, forecasting a 300% surge in corporate profits by 2026. This would mark the strongest annual profit expansion in Asian markets since the post-1999 Asian financial crisis recovery.

Goldman's strategists wrote, 'Memory chips are experiencing record supply gaps,' with surging DRAM and NAND demand from hyperscale data center investments driving sharp price increases.

JPMorgan twice raised its target price for South Korean stocks within a month, pushing the benchmark target to 9,000 points and the bull-case scenario to 10,000 points. Citigroup also lifted its target from 7,000 points to 8,500 points, citing 'strong semiconductor industry profit growth, proactive fiscal stimulus, and government measures to boost corporate value.'

The South Korean government itself was swept up in optimism. In July, the Ministry of Economy and Finance revised its 2026 GDP growth forecast from 2.0% to 3.0%, citing 'strong chip exports and fiscal stimulus,' and projected a record current account surplus of $290 billion for the year.

At the time, few were willing to take 'AI bubble' warnings seriously. While the Bank of Korea acknowledged the existence of 'AI bubble theories' in its February economic outlook report, it still judged that 'the semiconductor boom will persist for a considerable time.' This top-down optimistic consensus sowed the seeds for the subsequent panic.

Global Tech Stock Revaluation and Earnings Disappointment

The turning point came from the loosening of valuation logic in the global tech sector.

Over the past year, AI concepts had driven sustained gains in global tech stocks, with South Korean semiconductor firms—key beneficiaries of the AI supply chain—seeing rapid share price and valuation increases. However, as markets began to reassess the profitability of AI commercialization, questions arose about capital expenditure rhythms at major tech firms and the sustainability of semiconductor demand.

On July 29, SK Hynix's second-quarter results fell short of market expectations, becoming another straw that broke the market's back. That day, SK Hynix's American Depositary Receipts plummeted nearly 9%, with local shares following suit, triggering concentrated selling by investors. Overnight weakness in U.S. semiconductor stocks further fueled pessimism.

Kim Yong-gu, a researcher at Yuanta Securities Korea, cut to the heart of the issue: 'Current market capital flows and price trends are dominated by pessimistic expectations rather than fundamental factors like corporate earnings and value. Even if some leading firms have strong growth potential, reversing the overall market downtrend is difficult.' This means the market's pricing mechanism has shifted from 'earnings-driven' to 'emotion-driven,' and once sentiment turns, its self-reinforcing downward momentum becomes far more dangerous than fundamental deterioration.

The Bank of Korea's July report to the National Assembly also signaled caution. While acknowledging that AI and related infrastructure investments would sustain semiconductor industry growth for an extended period, it warned of 'downside risks due to skepticism about AI profitability, cutbacks in investments by major tech firms, and energy supply bottlenecks.'

The subtlety of this report lay in its refusal to deny the semiconductor sector's long-term prospects while implying that short-term valuations had already priced in overly optimistic assumptions.

A Market Held Hostage by Two Companies

If global tech stock corrections were the trigger, South Korea's own structural vulnerabilities were the powder keg.

The South Korean stock market's most fatal flaw is its extreme concentration. Samsung Electronics and SK Hynix, the two memory chip giants, account for over half of the KOSPI index's weight.

This means the KOSPI's performance is not fundamentally a barometer of South Korea's economy but a leveraged expression of memory chip industry sentiment. When global capital concentrate (Note: ' concentrate ' is translated as 'concentrated' in context) selling of tech stocks occurs, the South Korean market has virtually no buffer mechanism to absorb the shock.

This concentration is an advantage during rallies but a disaster during declines. Phillip Wool, portfolio management director at Rayliant Global Advisors, put it bluntly: 'For most investors, especially those who recently entered the South Korean market due to memory chip trades, the biggest challenge is that the easy money under this theme has already been made.' His fund has been taking profits on South Korean AI stocks and is now underweight on SK Hynix and Samsung Electronics.

A more conceal (Note: ' conceal ' is translated as 'subtle' in context) but equally dangerous issue is the negative feedback loop between foreign capital participation and the 'exchange rate-asset' dynamic. In the first half of the year, foreign investors net sold ₩148.3 trillion ($111 billion) worth of South Korean stocks, a record high for the period. Foreign selling of Korean stocks means conversion of won into dollars flowing out of South Korea, weakening the won and further reducing the attractiveness of won-denominated assets to remaining foreign investors, prompting more capital flight—a self-reinforcing vicious cycle.

By early October, foreign ownership of Samsung Electronics had fallen to 46.38%, the lowest since the 2008 financial crisis. SK Hynix's foreign ownership rate also dropped from a long-held level above 50% to 49.59%. Yuanta Securities' researcher summed it up with cold clarity: 'We confirm again that strong earnings alone cannot reverse foreign capital flows. Geopolitical events themselves will not directly prompt foreign capital to return.'

This means that even as Samsung Electronics reported a record ₩107 trillion ($80 billion) in operating profit for the third quarter, foreign selling continued unabated. The divergence between earnings and stock prices reflects deep-seated investor fears of a 'peak in the memory chip cycle'—a fear that, once formed, does not easily dissipate due to a single quarter's profit figures.

When Retail Investors Become Collateral Damage in the Panic

If foreign capital withdrawal is a 'slow knife cutting flesh,' forced liquidations of leveraged positions are a 'fast knife slicing through bone'—with every cut drawing blood.

In May 2026, the Korea Exchange approved the listing of the first 16 single-stock 2x leveraged ETFs, with underlying assets concentrated on Samsung Electronics and SK Hynix. This product design rapidly ignited retail speculative fervor amid the AI boom. The 16 leveraged ETFs saw their assets under management surge from ₩4.9 trillion to a peak of ₩16 trillion within a month of listing.

Margin financing in South Korea skyrocketed by about 75% from the start of the year to late June, reaching a record ₩29.8 trillion on June 24. Retail trading accounted for up to 48% of KOSPI market volume in January, making retail investors the most fervent participants in this rally.

Leverage amplifies everything—gains on the way up, losses on the way down. When the market abruptly turned south in July, forced liquidations of leveraged positions triggered a brutal 'panic effect.' South Korea's volatility index, VKOSPI, surged to 97.99, its highest level since records began in 2009. Citigroup estimated that by late July, South Korean retail investors had lost $38.7 billion on leveraged ETFs alone.

Official South Korean statistics show that as of July 13, cumulative forced liquidations for the month reached ₩344.2 billion, with over 1.2 million leveraged retail accounts hitting margin call levels. Around 320,000–360,000 of these accounts were fully liquidated by brokers, with some even owing money to their brokers.

Choo Kyung-ho, South Korea's Minister of Economy and Finance, was forced to apologize publicly for 'launching ETFs without sufficient prudential assessment.' But apologies could not recover the evaporated wealth. A commentary from an international investment researcher at a public fund proved telling: 'The South Korean stock market, like overseas markets in Vietnam and India, is a trading asset unsuitable for long-term holding.'

The 'False Prop' of Buybacks and Policy Dilemmas

Amid the market's despair, one force was seen as a 'lifeline': corporate buybacks.

Samsung Electronics and SK Hynix's combined ₩55 trillion ($41 billion) stock buyback program provided critical buying support during the collapse. JPMorgan data shows that buy orders from these two chipmakers accounted for the vast majority of the market's roughly $23 billion in buy orders last month.

Reports clarify (Note: ' clarify ' is translated as 'clearly' in context) indicate that the buyback programs of the two giants are 'nearing completion,' which may 'exacerbate concerns.' When the market's largest—and final—systematic buyers exit, South Korean stocks will face a starker supply-demand imbalance: sellers remain, but buyers are scarce.

The Bank of Korea has raised interest rates twice since July to 3.0%, with UBS expecting another 25 basis point hike in December. The reason lies in inflation pressures: the Bank of Korea projects that amid Middle East uncertainties, inflation may persist above policy targets, necessitating continued tight monetary policy. This means the South Korean central bank cannot provide liquidity support to the stock market through rate cuts—between inflation and asset prices, it has chosen the former.

South Korea's finance minister stated that market stabilization measures would be taken if necessary amid high global bond yields. However, the specifics, scale, and timing of these measures remain vague promises. After experiencing the burst of a leverage bubble fueled by policy, investor trust in policy rhetoric has significantly eroded.

Looking back from October 2026, the South Korean stock market's collapse was not an unforeseeable 'black swan' but rather the concentrated release of a series of predictable risks under specific conditions.

In September, UBS lowered its 12-month KOSPI target from 8,800 points to 8,000 points, reducing the implied price-to-earnings ratio from 8x to 7x, citing 'rising interest rates, a stronger won, and higher oil prices.' This report conveyed a cautious signal: while earnings growth in the memory sector remains strong, consensus expected EPS revisions—a key market driver—have begun to decline, and 'macro headwinds are starting to be reflected.' UBS set a downside target of 5,100 points, implying significant further downside from current levels.

No one can precisely predict where the market bottom lies. What is certain is that for South Korea's stock market to truly emerge from this crisis, it needs more than just another surge in memory chip prices—it requires a profound rethink of market structure, product design, and investor protection.

When a central bank must choose between inflation and asset prices, when regulators must apologize for a product they approved, and when retail investors' losses spill from brokerage accounts into psychiatric clinics, the lessons of this storm extend far beyond 'stocks are risky.'

The South Korean stock market's collapse is a mirror reflecting the AI narrative's return from frenzy to rationality—and the inevitable price paid for leverage-driven booms. For other markets equally enamored with chasing tech narratives and leveraged products, this mirror deserves a long, hard stare.