KOSPI: anatomy of a liquidation concentrated in…

On 28 July 2026, Samsung Electronics fell 13.4%, SK Hynix 14.7% and the KOSPI 10.8%. Concerns about AI infrastructure financing and Chinese competition supplied the initial shock. The structure of the Korean market did the rest: the two chipmakers jointly represented 52% of KOSPI market capitalisation on 15 July, up from 34% at the end of 2025. A fall in two stocks therefore became a fall in the index, then a mechanical constraint on leveraged products and credit-financed accounts. (Reuters, 28 July; Financial Services Commission, 16 July)

The word “liquidation” still covers three different events. A 2x ETF has to rebalance its exposure every day. A broker can sell a client’s shares when collateral becomes insufficient. It can also unwind a purchase when settlement is not paid on time. All three channels can sell together, but their statistics measure neither the same object nor the same period. Adding them would produce a dramatic and false number.

A 52% index built on two stocks

Concentration is more than a weighting detail. It is the condition that turns local leverage into an index problem. According to the Korean regulator, the combined share of Samsung Electronics and SK Hynix in KOSPI market capitalisation rose from 34% at the end of 2025 to 41% at end-April 2026, 49% on 26 May and 52% on 15 July. In less than seven months, their weight gained 18 percentage points. (FSC, 16 July 2026)

Concentration is calculated on KOSPI market capitalisation, not its number of companies. Primary source: FSC.

This dominance immediately transmits a memory-chip shock to every indexed portfolio. It also reduces the explanatory value of the headline level: “the KOSPI fell” can describe a broad crisis across Korean companies or, as here, an extraordinarily concentrated correction. A synthetic KOSPI excluding Samsung and SK Hynix is therefore the first useful counterfactual.

Leverage enters an already concentrated market

The regulatory calendar matters almost as much as the chart. On 21 April, the Korean government approved single-stock ETFs with maximum exposure of 200%. Eligibility notably required a stock representing at least 10% of market capitalisation and 5% of trading volume, plus an investment-grade credit rating. The regulator framed the reform as a way to close the gap with overseas products and reduce capital outflows to Hong Kong. (FSC, 21 April)

On 27 May, eight asset managers launched 16 ETFs: fourteen long 2x products and two inverse 2x products, split evenly between Samsung Electronics and SK Hynix. Two leveraged ETNs were added on the same day. Prior training and a KRW10 million minimum deposit applied, but the entire range targeted two stocks that already accounted for 49% of the index one day earlier. (FSC, 26 May)

For an individual, a 2x ETF can look safer than a margin account: the loss is capped at invested capital and the fund manages the derivatives. For the market, it nevertheless creates daily demand or supply that follows the underlying move. The wrapper pools leverage for investors, then concentrates rebalancing with the manager.

The daily mechanics of 2x

A 2x ETF targets twice the daily change in a stock, not twice its performance over several weeks. After a gain, it must increase exposure to start the next day at 200%. After a loss, it must reduce it. The rule makes it buy into gains and sell into losses. Daily compounding also creates decay when the market alternates sharply between gains and losses, even if the stock ends close to where it started. (FSC risk guide, 26 May)

The Korea Capital Market Institute estimated the size of this mechanism after launch. On 19 June, SK Hynix 2x ETFs had roughly KRW8.7 trillion in assets on the previous day and the share gained 2.9%. The theoretical rebalance represented about KRW260 billion of cash-equity purchases and KRW270 billion in futures. Over its study period, estimated cash rebalancing averaged 1.6% of Samsung’s daily trading value and 2.1% of SK Hynix’s. These are portfolio estimates, not transaction-level measurements.

The diagram separates the economic trigger from market amplifiers. A plausible loop does not establish causality on its own.

Two accounting cautions matter. ETF assets include inventory held by liquidity providers and therefore do not map entirely to final demand. Futures do not erase impact either: arbitrageurs can transmit an imbalance between derivatives and cash shares. Flow size matters, but timing and market depth matter just as much.

Three liquidation ledgers

The first ledger belongs to the leveraged fund. Selling after a fall is contractual rebalancing. It can be forced by the replication rule without any investor default and without a net outflow from the fund.

The second is margin credit, or 신용거래융자. The broker lends the cash used to buy securities and takes them as collateral. If the maintenance ratio falls below the required threshold and the client fails to add enough collateral, Korea Financial Investment Association rules allow the broker to sell. The national balance reached a record KRW38.63 trillion on 24 June, then fell to KRW34.37 trillion on 15 July, according to KOFIA data cited by Reuters. The KRW4.26 trillion drop measures total deleveraging, not forced sales alone. It also includes voluntary repayments and changes in balances. (Reuters, 20 July)

The third is an unpaid settlement receivable, or 위탁매매 미수금. The broker briefly advances the funds for a purchase that the client must settle. If payment fails, it sells. From 1 to 10 July, these forced counter-trades tied to unpaid receivables amounted to KRW425.8 billion, including KRW142.2 billion on 9 July. This KOFIA statistic, reported by SBS, covers neither all margin credit nor ETF rebalancing. (SBS, 14 July)

A product market capitalisation, a credit balance and a flow of forced counter-trades answer three different questions.

This breakdown changes the interpretation. The fall in the credit balance does show a leverage purge, but not its execution price. The unpaid-receivables statistic measures actual triggered sales, but for a narrow subset. ETF rebalancing can occur without investor redemptions. Liquidation is real, but no single public counter provides a consolidated total.

The July purge

By 15 July, the market capitalisation of the 16 leveraged products had risen from KRW4.4 trillion to KRW11.9 trillion since launch. Their daily trading value had increased from KRW10.4 trillion to KRW13.0 trillion. From 26 May to 10 July, the regulator calculated annualised volatility of 96% for Samsung and 113% for SK Hynix. (FSC, 16 July)

These figures make amplification plausible, but they do not prove the ETFs created the reversal. The KCMI study also observes a sharp rise in volatility at Micron, in the SOX index and across other global semiconductor shares around the same period. Expectations for AI spending, data-centre financing and memory competition therefore remain independent triggers. Our analysis of the global chip relapse documents this move outside Seoul.

The defensible causal statement is narrower: concentration transmitted almost the entire shock in two shares to the index; 2x ETFs added procyclical demand or supply; credit made some holders sensitive to the path of prices and collateral. Leverage can explain why the journey became so violent without explaining by itself why the market changed destination.

The regulator applies the brake

On 16 July, less than two months after launch, the FSC suspended new listings and advertising for single-stock products. It decided to raise the minimum deposit from KRW10 million to KRW30 million in cash, require an extra hour of training and increase the minimum trading unit from 1 to 20 shares. On 24 July, it brought forward the stronger cash requirement to 31 July. (FSC, 16 July; FSC, 24 July)

On 28 July, the regulator asked asset managers to spread rebalancing through the session instead of concentrating it at the close. It acknowledged the trade-off: a more dispersed execution may reduce instantaneous impact but increase tracking error if the stock moves before the close. The FSC also floated an individual limit, such as 20% of an investor’s financial assets, without adopting it at that stage. (FSC, 28 July)

This sequence forms a rare regulatory experiment. The April opening sought to repatriate demand that had moved to Hong Kong. The July brake admits that domesticating the product does not remove its microstructure risk. It only makes that risk more visible and more directly regulable.

A closing-auction hypothesis to test

A preprint published on 4 August pushes the analysis further. It argues that predictable end-of-day rebalancing lets other market participants buy or sell ahead of the ETFs, then transfer the position to them at a less favourable price. The loop would no longer be merely procyclical: it would be partly anticipated by the market.

This thesis is not established fact. The paper labels itself preliminary and incomplete, has not been peer reviewed and discloses AI assistance. Its wealth-transfer estimates depend on a counterfactual model. It nevertheless provides a falsifiable hypothesis consistent with the regulator’s concern over order concentration at the close.

Four tests would help settle it:

compare Samsung and SK Hynix returns in the final minutes with the rest of the session, before and after 27 May;
match predicted rebalancing flows against actual closing-auction and futures volume;
track a KOSPI excluding the two shares to separate broad Korean stress from concentration;
use Micron, Kioxia and the SOX as controls for the global chip cycle.

If the closing effect disappears, if the KOSPI without Samsung and Hynix falls just as much and if foreign peers follow the same path, the leverage explanation weakens markedly. If a gap appears precisely after launch, grows with product assets and recedes as execution is dispersed intraday, it becomes stronger.

Public data do not yet allow transaction-level consolidation of the three layers. The FSC publishes product market capitalisation and volumes. KOFIA publishes credit and counter-trades on receivables. KCMI reconstructs rebalancing from portfolios. None of these datasets links each order to the fund, credit account or arbitrageur that submitted it. Estimates of total liquidation must therefore remain attributed and accompanied by their method.

The robust diagnosis fits in one sentence: a global chip shock hit two shares that had become half the KOSPI, then distinct leverage layers could amplify its path. Concentration made the market fragile. 2x ETFs made part of demand mechanical. Credit turned volatility into a collateral constraint. Liquidation is not a rival explanation to the fundamental shock; it is the mechanism through which that shock could become a cascade.

For related plumbing, read our work on the Treasury basis trade and forced unwinds, the carry-trade guide and the definition of a margin call. For the sector trigger, see the stack of semiconductor constraints.

Sources

Limitations

Market moves quoted here are dated and sourced; they are not real-time prices. KCMI rebalancing flows are estimates based on portfolio structure. The decline in margin-credit balances does not measure forced sales alone. Unpaid settlement receivables cover a narrower scope than margin credit. The 4 August preprint is neither final nor peer reviewed. Finally, no public source reviewed for this article yet provides a consolidated register linking every July sale to its leverage layer.

KOSPI: anatomy of a liquidation concentrated in two stocks