A single-day crash of nearly 10% triggers four circuit breakers—a stock market stampede fueled by leveraged speculation across the entire population.

The most explosive event in the capital markets recently is undoubtedly the frequent circuit breakers in the Korean stock market: KOSPI plunged 9.99% in a single day, triggering a market-wide circuit breaker; four circuit breakers within the year set a historical record; Samsung and SK Hynix plummeted over 12%; trillions of won in leveraged positions collapsed in a chain reaction; foreign capital fled en masse; retail investors trapped after buying the dip with trillions. This crash is no accident—it's a textbook stock market disaster triggered by industrial distortion, nationwide leverage, high Fed interest rates, and catalytic news. Understanding the logic behind Korea's circuit breakers offers crucial lessons for A-share investments and helping retail investors avoid pitfalls.

I. First, reconstruct the full crash process: from manic rally to circuit breaker collapse in just a few days.

1. Extreme mania in the early stage, inflated bubble.
Previously, KOSPI surged wildly, breaking through the 9,000-point historical high from 8,000 points in just over a month, riding on AI memory chip rallies, a nationwide stock trading frenzy, and foreign capital inflows. Korean households moved savings into stocks, with many ordinary people emptying deposits and borrowing to buy stocks, creating an atmosphere of nationwide stock speculation. The market completely detached from fundamentals, driven purely by liquidity pushing the index upward.

2. The trigger was just a "stamp-less rumor document."
The immediate catalyst for the crash was only a draft discussion on stock capital gains tax that had not been finalized: rumors circulated that Korea would tax unrealized stock gains and unrealized real estate profits. The market panicked that funds would flow out of stocks significantly, leading to a low open and weakening trend in early trading. Combined with a pullback in U.S. tech stocks, renewed expectations of Fed rate hikes, and collective weakness in Asia-Pacific markets, multiple negative factors resonated, and the downward trend became unstoppable.

3. Two circuit breakers triggered in succession, leading to a deadly stampede:
- Morning session: KOSPI200 futures fell over 5%, triggering the Sidecar mechanism, suspending all programmatic trading for 5 minutes, temporarily halting quantitative selling pressure.
- Afternoon session: The KOSPI index plunged over 8% and maintained for 1 minute, triggering a Level 1 market-wide circuit breaker, suspending all stocks for 20 minutes. This was the fourth circuit breaker this year and the tenth in history (only six in the past 26 years, with four in a single year in 2026 being a spectacle).
- After the circuit breaker, panic fully spread, with concentrated sell orders flooding in. The market closed down 9.99%, a single-day drop of 910 points, the largest single-day decline in nearly three decades. Leading heavyweight Samsung Electronics fell 12.31%, SK Hynix dropped 12.47%, and the two memory giants directly crashed the entire index.

4. Extreme divergence: foreign capital fled frantically, retail investors trapped after buying the dip with trillions.
Foreign investors dumped over 2 trillion won (about $1.3 billion) in a single day, concentrating on selling core semiconductor heavyweights. In contrast, Korean retail investors went against the trend and aggressively bought the dip, recording a net purchase of 8.52 trillion won (about 37.6 billion RMB), setting a historical daily record for retail buying in the Korean stock market. These dip-buying funds were all deeply trapped on the same day, and they will face a second wave of selling from leveraged liquidations.

II. The four core underlying root causes of Korea's frequent circuit breakers (the trigger is just the surface; the root causes were already in place).

1. Extremely distorted index structure: semiconductors hijack the entire stock market, with no buffer.
The Korean stock market is an extremely singular chip-dependent market: Samsung Electronics, SK Hynix, and Samsung-affiliated companies together account for over 50% of the KOSPI index weight. The entire market trend is completely tied to the AI memory chip cycle.
When AI is booming, the index surges; once global memory demand cools and chip price increase expectations fade, the two giants easily drop 10%+, causing the index to crash 8% or more. Without sectors like consumer, healthcare, or financials to hedge, the index inherently carries a "crash gene." This is the congenital flaw that makes Korea's stock market prone to circuit breakers.

2. Widespread high leverage across the population is the core accelerator of circuit breakers (fatal risk).
This is the most critical culprit in the crash: In late May, Korea approved 16 2x leveraged ETFs on single stocks, all linked to the two chip giants Samsung and SK Hynix. Retail investors could buy these 2x bullish products with one tap on their phones, without needing margin accounts or risk controls.
In just over a month, the size of these leveraged ETFs surged from $3 billion to $9.1 billion, with over 90% of holders being ordinary retail investors and a weekly turnover rate of 200%. This essentially meant the entire population was betting on chip stocks with leverage.
Once stock prices fell slightly, the 2x leveraged products triggered a chain of forced liquidations: stock price drop → leveraged positions blow up and forced selling → further stock price decline → more leveraged accounts blow up, forming a vicious negative feedback loop. Within an hour, massive sell orders flooded in, smashing the index to the circuit breaker level. Regulators even publicly regretted approving these leveraged products afterward.

3. Foreign ownership is too high, making it easy for collective flight under high Fed rates.
Foreign investors hold over 35% of the Korean stock market, and over half of semiconductor heavyweights are held by foreign investors, making the market foreign-dominated in pricing.
With the Fed maintaining high interest rates and expectations of rate hikes resurging this year, the U.S. dollar continues to strengthen, and global risk assets flow back to U.S. Treasuries. Once foreign investors collectively turn bearish and dump Korean stocks without sufficient buying support, the index can quickly cliff-dive. Coupled with the simultaneous depreciation of the Korean won, foreign investors have a stronger incentive to exit after selling, further amplifying the decline. This has been an external driver behind the frequent circuit breakers in recent years.

4. Extreme emotional behavior among retail investors: greed in rallies, panic in crashes amplifies volatility.
Retail investors account for over 60% of trading volume in the Korean stock market, making them the dominant trading force: during an uptrend, they blindly chase highs and add positions, fueling bubbles; during a downturn, they panic in a stampede to cut losses, and negative rumors are amplified infinitely (an unenacted tax draft could crash the index 10%). Additionally, retail investors lag in buying the dip—buying more as prices fall only delays the cleansing process and prolongs the downtrend, turning circuit breakers from an occasional event into a norm.

III. Four hard-hitting lessons from Korea's circuit breakers for A-shares and ordinary investors (most worth saving).

Lesson 1: Absolutely stay away from high-leverage trading. Leverage is poison—small gains in bull markets, capital wipeout in bear markets.
The outcome of Korea's 2x leveraged ETFs perfectly demonstrates: leverage only amplifies gains but infinitely amplifies losses. In volatile or bear markets, leverage equals an accelerant for blow-ups.
A-shares have always strictly controlled margin trading and leveraged ETFs, limiting high leverage and tightening margin requirements, essentially to preemptively avoid Korea's leveraged stampede-style circuit breakers. Ordinary retail investors should never borrow money to trade stocks or touch any product with 2x or higher leverage. This is the bottom line to avoid 80% of major losses.

Lesson 2: Never put all eggs in one sector; balanced allocation is key to withstanding downturns.
Korea suffered from "betting on a single semiconductor track," with the index having almost no defensive sectors. In contrast, A-shares have multiple sectors like financials, high-dividend stocks, consumer, healthcare, and cyclical sectors to hedge. Even if semiconductors pull back, low-valuation sectors can support the index, making it difficult to see a single-day crash of 8%+ that triggers a circuit breaker.
For personal investment, the same logic applies: don't go all-in on one industry or individual stock. A balanced allocation of growth and value can weather extreme black swan events.

Lesson 3: Foreign capital flows are just short-term disturbances; domestic long-term capital is the market's anchor.
Korea's biggest weakness is the small size of domestic long-term capital (pension funds, insurance). They don't support the market when it rises and tend to sell when it falls. In recent years, A-shares have been steadily growing public funds, social security, insurance, and industrial long-term capital to reduce reliance on foreign capital. Even if northbound capital flows out short-term, domestic funds can take over, preventing extreme circuit breaker scenarios.

Lesson 4: The destructive power of negative rumors far exceeds that of actual policies. In a news-driven market, always keep your hands steady.
The trigger for Korea's crash was just a discussion draft; the policy never materialized, yet the market had already dropped 10%. Capital markets always "buy the rumor, sell the fact." The panic from vague negative news is far more damaging than the actual implementation of a policy. When encountering various rumors and "Xiaowen" (unofficial news reports) in the future, avoid panic selling. First, verify the authenticity of the news, and avoid being driven by emotions to chase highs and cut lows.