South Korea’s stock market came under intense selling pressure during Thursday’s (August 6) session, just one day after a sharp rebound, with the benchmark KOSPI index plunging more than 5% at one point and breaching the 6,300-point level, forcing the Korea Exchange to once again activate its “program trading halt mechanism” (SIDECAR). This marks the second time the mechanism has been triggered in the last six trading sessions, underscoring the extreme boom-and-bust pattern gripping South Korean equities.

According to data from the Korea Exchange, at 10:18:12 a.m. on August 6, as KOSPI 200 index futures prices had fallen more than 5% from the previous trading day and sustained that level for one minute, the exchange formally issued a five-minute halt on programmatic sell orders in the KOSPI market. This is the first sell-side SIDECAR triggered since July 29, bringing the total number of SIDECAR activations in the KOSPI market this year to 46 (24 sell-side SIDECARs and 22 buy-side SIDECARs).

As of 10:30 a.m., the KOSPI index stood at 6,258.76 points, down 339.50 points, or 5.15%, from the previous session’s close of 6,598.26 points. Market participants described the recent volatility as having reached an extreme where “SIDECAR has become a daily occurrence.” Just the previous trading day, the KOSPI had triggered a buy-side SIDECAR after surging more than 3%. Earlier, on July 31, the index had skyrocketed by 1,001.89 points, or 17.91%, in a single day—the largest one-day point gain and percentage increase in history. Yet, just days later on August 3, the index gave back 5.12%, highlighting the extreme instability in market sentiment.

The notion that “SIDECAR has become a daily occurrence” is evident from the triggering record over the past two weeks:

DateEventChangeSIDECAR TypeJuly 29Intraday plunge triggers circuit breaker—Sell-side SIDECARJuly 31Single-day surge, record point gain+17.91% (1,001.89 pts)Buy-side SIDECARAugust 3Rally reverses, sharp decline next day-5.12%—August 5 (prior session)Index surges again+3% or moreBuy-side SIDECARAugust 6 (today)Semiconductor heavyweights lead decline-5.15%Sell-side SIDECAR (46th this year)

▲ KOSPI’s boom-and-bust trajectory under the SIDECAR circuit breaker mechanism over the past two weeks; cumulative triggers this year have reached 46 (24 sell-side, 22 buy-side).

The culprit behind this sell-off was massive dumping by foreign investors and a broad-based collapse in semiconductor heavyweight stocks. Data shows that foreign investors net sold a staggering ₩1.48 trillion (approximately $1.0 billion) during the morning session, far exceeding the ₩1.44 trillion (approximately $1.0 billion) in net buying by retail investors and institutional purchases, making foreign selling the decisive force crushing the index.

The two semiconductor titans saw their share prices tumble in tandem, becoming the epicenter of the broader market rout. Samsung Electronics (005930) plunged 6.50% intraday, with its share price briefly falling below ₩230,000 (approximately $162.18). SK Hynix (000660) suffered an even more brutal decline, tumbling more than 9.35% at one point, with its share price dropping to ₩1.51 million (approximately $1,066.16). Market sources indicated that SK Hynix briefly hit the 30% daily limit down at the opening of Nextrade pre-market trading; although volume was extremely thin at the time and the stock quickly recovered some losses, selling pressure re-emerged once the main trading session began, signaling deeply divided views on the company’s outlook.

Beyond the two leaders, other semiconductor-related stocks were also battered. SK Square (402340) plunged 10.81% intraday, Samsung Electro-Mechanics (009150) tumbled 10.55%, and Samsung Electronics preferred shares fell 5.27%. With major heavyweight stocks uniformly heading lower, the overall KOSPI market was exceptionally weak, with only 265 stocks advancing compared to 610 decliners.

The tech-heavy KOSDAQ index was not spared either, falling 18.03 points, or 2.25%, to 781.56 points during the same period. Although retail investors net bought ₩233.9 billion (approximately $164.9 million), foreign and institutional investors net sold ₩212.2 billion (approximately $149.6 million) and ₩21.5 billion (approximately $15.2 million), respectively, weighing on the index. Among KOSDAQ heavyweights, EcoPro fell 2.19%, EcoPro BM dropped 2.75%, HLB declined 2.29%, and Jusung Engineering tumbled 6.30%.

Regarding the roller-coaster ride in South Korean equities this week, market analysts suggest it is not entirely driven by clear macroeconomic headwinds. In fact, crude oil prices fell sharply this week amid progress in Iran-Oman negotiations over the reopening of the Strait of Hormuz, which should help ease inflation and interest rate expectations. Meanwhile, the overall tone of the U.S. tech earnings season remains positive, with strong results from key companies like Palantir indicating that capital expenditure and demand in the artificial intelligence (AI) sector remain robust. Yet, South Korean stocks accelerated their decline in the absence of significant negative catalysts, reflecting widespread fragility in global market sentiment.

Some analysts point out that investors harbor deep-seated doubts about the profit outlook for memory chip giants Samsung Electronics and SK Hynix. While earnings forecasts for both companies remain strong, the market fears these expectations may ultimately prove “too good to be true.” This skepticism has deepened particularly after reports emerged of yet another hedge fund suffering massive losses from technology stock positions, intensifying concerns about whether tech stocks have truly bottomed.

Han Ji-young, a researcher at Kiwoom Securities, noted that despite improvements in geopolitical and macroeconomic conditions, upward momentum has clearly stalled due to weakness in the U.S. Philadelphia Semiconductor Index overnight and profit-taking pressure following the recent short-term surge in South Korean equities. The market is now transitioning into a “consolidation and rotation” phase characterized by sector rotation.

The backdrop to this violent volatility is the extreme leveraged capital frenzy that South Korean equities experienced over the past several months. Retail investors had been aggressively betting on Samsung Electronics and SK Hynix through margin trading and single-stock leveraged ETFs, propelling the market to historic highs. However, as stock prices reversed in July, these highly leveraged products triggered catastrophic forced liquidations. According to data from Goldman Sachs, the assets under management of South Korean leveraged ETFs have shrunk dramatically from a peak of $53 billion in June, while retail margin loan balances have also declined significantly.

Yet, amid the prevailing pessimism, Goldman Sachs has bucked the trend with an optimistic forecast. Tim Moe, Goldman Sachs’ chief Asia-Pacific equity strategist, reiterated the firm’s 12-month KOSPI target of 12,000 points, implying roughly 80% to 90% upside from current levels. Goldman’s core thesis is that AI-driven memory chip demand will create a “stronger and longer” earnings cycle, and current market pricing does not reflect a severe memory chip shortage that could persist through 2030. Goldman forecasts that South Korean corporate earnings will grow 32% this year and another 35% next year, with the KOSPI currently trading at just 5.1 times forward earnings, well below historical averages.

Goldman also noted that after the July deleveraging episode, forced liquidations by retail investors and tighter leverage rules imposed by regulators have left market positioning “much cleaner,” laying the groundwork for a future rebound.

However, not everyone is so optimistic. Shuli Ren, a columnist for a U.S. financial media outlet, bluntly stated that South Korean equities are increasingly becoming an “uninvestable market.” She pointed out that the KOSPI tumbled roughly 40% from its peak in just 27 trading days, and there have already been 33 trading days this year with single-day moves exceeding 5%, far higher than Japan’s four days and Hong Kong’s zero. Even though the KOSPI trades at a price-to-earnings ratio of only about 5.5 times—a 10-year low—such extreme volatility is enough to deter international capital. She criticized the proliferation of single-stock leveraged ETFs and the South Korean government’s hasty market intervention measures, which risk damaging market credibility and making the market structure even more fragile, potentially following the path of certain markets that have been marginalized by international capital due to policy risks.

Indeed, the frequency of KOSPI SIDECAR triggers this year has already set a historic record. According to a July 30 report by the Korea Times, data from the Korea Exchange showed that the number of SIDECAR triggers on the KOSPI this year (as of that date) had reached 43, far exceeding the previous record of 26 set during the 2008 global financial crisis. Including 29 triggers on the KOSDAQ, the total number of SIDECAR activations across the two markets this year has reached 72. Ahn Dong-hyun, a professor of economics at Seoul National University, noted that while SIDECAR helps temporarily stabilize market sentiment, questions remain about whether it can truly reduce volatility. He warned that without addressing structural issues such as excessive concentration in semiconductor stocks, the expansion of leveraged ETFs, and the high proportion of retail investors, circuit breaker mechanisms are unlikely to cure the root cause—a view that aligns with the recent regulatory storm surrounding single-stock leveraged ETFs in South Korea.

Mechanisms designed to address severe futures market volatility vary across markets:

MarketMechanism NameTrigger ThresholdResponse MeasureSouth Korea KOSPI (introduced 1996)SIDECARFutures price change exceeds 5% for 1 minuteHalt programmatic sell orders for 5 minutesUnited States (introduced 1988, abolished 1999)SidecarModeled after 1987 Black Monday experienceSEC deemed it could impede price discovery; abolished, replaced with market-wide circuit breakers and individual stock limitsJapan TSEFutures circuit breakerNikkei 225 futures hit daily price limitSuspend trading for at least 10 minutes, then gradually widen limitsHong KongVolatility Control Mechanism (VCM)Major stock matching price deviates from 5-minute reference price by thresholdNo full suspension; trades matched within limited price band for 5 minutes

▲ Sources: Korea Times (July 30, 2026), Korea JoongAng Daily (July 28, 2026)

The market’s current focus is on when the frenzied foreign selling might ease and whether semiconductor stocks can find support after this severe correction. The SIDECAR trigger can only provide a brief cooling-off period; the market’s ultimate direction will depend on whether investors regain confidence in the long-term AI and memory chip earnings narrative.