The KOSPI closed down 5.47%, while SK hynix plunged 10.09%. The core conflict was the simultaneous resonance of three factors: foreign capital outflows, China’s advances in memory technology, and doubts over financing for AI capital expenditures. As a proxy asset for the AI memory trade, the KOSPI’s vulnerability was systematically amplified.

【Part One: Events and Background】On October 13, South Korea’s KOSPI Index closed down 348.9 points at 6035.34, a decline of 5.47%. It fell more than 7% at one point during the session, prompting the Korea Exchange to activate the SIDECAR circuit breaker and suspend programmatic selling. SK hynix plunged 10.09%, Samsung Electronics fell 7.38%, and the Nikkei 225 Index declined 1.8%. Spot gold broke above $4,200, the 10-year U.S. Treasury yield fell to 5.20%, and Brent crude dropped to $105.58.
Key background: Foreign capital outflows have reached an extreme historical level. From the beginning of the year through October 12, foreign investors had cumulatively net sold approximately 199 trillion Korean won (about ¥992.5 billion), while net sales exceeded $6 billion in October alone. Samsung Electronics’ foreign ownership ratio fell to 46.38%, the lowest since the financial crisis in January 2008; SK hynix’s foreign ownership ratio fell below 50% to 49.59%.
China’s breakthroughs in memory technology constitute a direct shock.
ChangXin Memory Technologies announced key progress in its 4F² DRAM architecture and is expected to launch DDR5 RDIMM server memory by year-end. Its DRAM revenue share has reached 10%, ranking fourth globally. A Counterpoint research vice president judged that “the question is no longer whether it can enter the global top three, but when.”
Doubts over financing for AI capital expenditures erupted across the market.
Broadcom CEO Hock Tan warned that “the biggest constraint is capital, not chips,” while NVIDIA CEO Jensen Huang and Intel CEO Lip-Bu Tan simultaneously voiced concerns over financing costs. Ray Dalio had previously warned that the AI bubble was “nearing the bursting point.”
Market expectations vs. reality: The market had previously viewed the KOSPI as a proxy asset for the AI memory supercycle, but the three factors resonated simultaneously—foreign capital outflows are a persistent trend, ChangXin’s breakthrough is a catalyst, and financing doubts are a sentiment amplifier—systematically magnifying the KOSPI’s vulnerability.

【Part Two: Analytical Framework】Affected assets and direction:
KOSPI Index: Broke below the 200-day moving average and fell by one-third from its June high; direction is bearish.
SK hynix: HBM share fell from 64% to 50%, while its general-purpose DRAM business faces competition from ChangXin; direction is neutral to bearish.
Samsung Electronics: Foreign ownership fell back to 2008 levels. Its scale advantage provides a buffer, but passive selling continues; direction is neutral to bearish.
Spot gold: Broke above $4,200 as risk aversion intensified across the board; direction is bullish.
ChangXin Memory Technologies supply chain: China’s domestic DRAM breakthrough is driving demand for equipment, materials, and packaging and testing; direction is bullish. Transmission logic: ChangXin’s 4F² breakthrough → the pricing power of the three major memory makers faces erosion → foreign investors accelerate withdrawals from South Korean stocks → the KOSPI falls below its 200-day moving average, triggering programmatic selling → SIDECAR circuit breaker → compounded by doubts over AI capital expenditure financing → safe-haven funds flow into gold and U.S. Treasuries → a “sell → won depreciation → sell again” negative feedback loop forms
Bull-bear comparison: The bulls argue that the AI-driven DRAM supply-demand gap is still widening, Micron’s DRAM selling prices rose more than 60% quarter-on-quarter in Q1, ChangXin’s yield rate and customer certification still require 12 to 18 months of verification, and Samsung’s foreign ownership ratio of 46.38%, near the 2008 crisis level, leaves room for an oversold rebound;
The bears argue that foreign net sales exceeded $6 billion in October and the trend has not stopped, the approximately $41 billion in buyback demand from the two major chip giants is about to disappear, the KOSPI has fallen by one-third from its June high and broken below its 200-day moving average, and won depreciation and foreign capital outflows are forming a negative feedback loop.
Cross-market linkage check: (1) South Korean stocks and Taiwanese stocks—the taiwan Weighted Index has risen 70% year to date and outperformed the KOSPI by approximately 23 percentage points last quarter, with AI capital structurally migrating from South Korea to taiwan; (2) AI debt and U.S. Treasuries—hyperscalers’ capital expenditures are expected to exceed $1.2 trillion in 2027, while operating cash flow will total only about $1 trillion, leaving a financing gap of approximately $200 billion, with AI debt competing with U.S. Treasuries for duration buyers.
Policy sensitivity: High.
The Bank of Korea faces pressure to raise interest rates, leaving limited room for monetary easing and further weakening the appeal of South Korean stocks.

【Part Three: Scenario Analysis】
Scenario One: Foreign outflow slows and the market moves within a range (40% probability): Triggering conditions are a stable won exchange rate and memory chip prices remaining high.
Path: Monthly foreign net sales fall from $6 billion to below $3 billion, the KOSPI fluctuates within the 5800 to 6200 range, and the market awaits signals of the next round of memory chip price increases.
Scenario Two: Accelerated foreign withdrawals trigger a second bottom (35% probability): Triggering conditions are continued rises in global bond yields or a further slowdown in memory chip price gains.
Path: Foreign selling accelerates, the won depreciates further, retail margin balances fall from 33 trillion Korean won to below 28 trillion Korean won, and the KOSPI drops below 5800. Historical comparison: The KOSPI rebounded rapidly after plunging during the COVID-19 crisis in March 2020, but foreign ownership was much higher then and synchronized global central-bank easing provided liquidity. The effective limitation now is that the Bank of Korea faces pressure to raise interest rates, leaving far less room for monetary easing than in 2020.
Scenario Three: Stronger-than-expected memory chip demand is confirmed, driving foreign capital back (25% probability): Triggering conditions are HBM4 orders for 2027 significantly exceeding expectations or Samsung formally entering NVIDIA’s HBM supply chain.
Path: Foreign investors reassess the durability of the memory chip supercycle, Samsung and SK hynix receive valuation re-ratings, and the KOSPI challenges 6500 again.

【Part Four: Key Variables】
Monthly foreign net outflows: October net sales currently exceed $6 billion; a decline to below $3 billion would indicate easing selling pressure.
Samsung Electronics’ foreign ownership ratio: Currently 46.38%, the lowest since January 2008; a further decline below 46% would trigger additional selling by passive funds.
Mass-production yield of ChangXin’s 4F² DDR5 RDIMM: The gap between the technology announcement and successful mass production will determine whether the shock is “expectation-driven” or “structural.” A yield breakthrough above 80% would establish commercial viability.
Won-U.S. dollar exchange rate: Foreign withdrawals and won depreciation are creating a negative feedback loop; exchange-rate stabilization is the key point for breaking the cycle.

【Part Five: Reverse Test】The most likely error is underestimating Samsung Electronics’ valuation buffer. Samsung Electronics’ forward P/E ratio is approximately 4 to 5 times, well below Micron Technology’s 10.2 times, representing a valuation discount of more than 50%. Samsung’s third-quarter operating profit reached a record 107.4 trillion Korean won; if foreign investors believe the valuation already fully reflects bearish expectations, short covering may occur.
Revision signal: When monthly foreign net outflows turn into net inflows and Samsung’s share price stabilizes, South Korean stocks should be reclassified from “continuing to bleed” to “building a valuation floor.”

【Part Six: Assessment and Uncertainty】
Core assessment: The essence of the South Korean stock plunge is the structural flaw of the KOSPI as a “proxy asset for the AI memory trade”—more than half of its weighting is concentrated in two memory chip companies, while global public funds’ compliance limits make passive selling a persistent source of pressure. ChangXin’s 4F² breakthrough is a catalyst rather than the root cause, and the negative feedback loop formed by foreign withdrawals and won depreciation will be difficult to break in the short term.
Confidence: Medium-high.
Supporting reasons include foreign ownership ratios falling back to 2008 levels, year-to-date net sales reaching 199 trillion Korean won, and the KOSPI breaking below its 200-day moving average and triggering programmatic selling; mitigating reasons include Samsung Electronics’ significant valuation discount and continued resilience in memory chip demand. Failure condition: Monthly foreign net outflows turn into net inflows and Samsung regains HBM orders.
Validity period: 3 to 6 months.

【Part Seven: Summary】The core conflict is that the KOSPI is being treated as a proxy asset for the AI memory supercycle, while AI capital is migrating to taiwan, whose industrial-chain positioning is more diversified. Meanwhile, the concentration of more than half of the index’s weighting in two companies makes passive selling a persistent source of pressure, and the negative feedback loop formed by foreign withdrawals and won depreciation will be difficult to break in the short term.
Forward-looking assessment: The foreign ownership ratio is the core indicator for determining whether selling pressure has bottomed. A stabilization and recovery in Samsung Electronics’ foreign ownership ratio from 46.38% is a prerequisite for sentiment recovery in South Korean stocks; the actual mass-production yield of ChangXin’s 4F² architecture is the hard indicator for assessing the intensity of China’s memory-sector shock, and the gap between the technology announcement and successful mass production will determine the nature of the shock; China’s taiwan is structurally replacing South Korea, with the overweight ratio for Taiwanese stocks in a Bank of America survey standing at 1.6 times that for South Korean stocks, meaning the capital migration is not a short-term rotation.
Track just one variable: whether Samsung Electronics’ foreign ownership ratio rises back above 47% before the first quarter of 2027—this is the hardest indicator for determining whether foreign selling pressure has bottomed.

View Original

This page contains third-party content and does not constitute any advice, nor does it represent Gate's endorsement of such views. For details, please see disclaimer.