About 1.2 million everyday investors in South Korea were hit with margin calls during a stock market crash that shook Asian markets, MarketWatch reported on July 17, 2026. That number is more than 3% of the country's adult population.

A margin call is what happens when you borrow money from your broker to buy stocks, and the value of those stocks falls far enough that the broker says: pay up or we'll sell your shares. When lots of people get that notice at the same time, they all have to sell — and that pushes prices down even more, causing even more margin calls. It's a cycle that can turn a bad day into a full-blown crash.

This crash did not come out of nowhere. South Korean retail investors — nicknamed "ants" because they move together in large numbers — had been borrowing heavily to buy stocks and a type of investment called a leveraged ETF through the first half of 2026. A leveraged ETF is designed to multiply the daily gains of a stock index. If the index goes up, the ETF goes up twice as much. But if the index falls, the ETF loses twice as much, too. Reuters reported on June 8 that these borrowed investments had reached a record high, with investors afraid of missing out on gains even as semiconductor stocks — a big part of South Korea's main stock index, the KOSPI — were already falling. The same Reuters reporting noted that margin debt, the money investors borrow to buy stocks, had risen significantly before June 2026.

On June 23, South Korean regulators publicly warned investors against borrowing to trade on the KOSPI. That same day, the KOSPI dropped nearly 10%, according to Reuters. A drop that large in a single day automatically triggered margin calls across thousands of accounts, forcing more selling that continued through July.

Foreign investors were already leaving. Reuters reported on July 14 that foreign investors had pulled a record of nearly $110 billion out of South Korean stocks over the course of 2026. South Korean retail investors bought 13.2 trillion won of stocks during the downturn, partly filling the gap left by foreign sellers. This kind of pattern — big institutions selling while everyday investors buy — also happened during China's 2015 market crash and the U.S. meme-stock frenzy in 2021.

The numbers show investors growing more confident as prices fell. In February, Bloomberg reported that South Korean retail investors had $77 billion in cash ready to put into local stocks. They spent that cash into a falling market. By the time regulators issued their June 23 warning, borrowed money had climbed to record levels. The sequence — spending cash, borrowing more, getting a warning from regulators, a sharp drop, then mass margin calls — is one that researchers have seen play out before.

What sets this event apart is how widespread it was. More than 3% of a country's adults getting margin calls in one crash means leverage had reached deep into the population. In most markets, margin calls affect a small group of active traders. The South Korean figure suggests many investors may not have fully understood how borrowing to invest can amplify losses.

Another factor is the makeup of the KOSPI itself. It is heavily weighted toward semiconductor and technology companies, which are naturally volatile. When the global chip market turned down, those stocks fell hard. And because leveraged ETFs are designed to multiply daily returns, a sustained downturn can produce losses that grow faster than investors expect, as the funds are forced to make additional trades to stay on target.

The bigger picture here is that two things are happening at once. The $110 billion that foreign investors pulled out is the more important number for the broader economy. It signals that global investors are rethinking their commitment to Korean stocks for reasons that go beyond any single sector. The margin-call figure, on the other hand, is about the cost to ordinary households — significant for the people involved, but a result of the selloff, not the root cause of it.

The open question is whether the 13.2 trillion won that retail investors spent during the crash reflects genuine long-term confidence or money that is now stuck in a falling market. The "ants" have bought aggressively against institutional selling before. Whether they keep buying if prices fall further — or whether the July margin calls force them to pull back — will shape Korean markets for the rest of 2026.