South Korea Halts Stock Trading as KOSPI Plunges 8.5% in Global AI Sell-Off

South Korea’s stock market stopped trading on Friday, 6 November 2026, after its main index plunged more than 8% within minutes of the opening bell. It was the sharpest shock yet in a global sell-off of technology shares that has already wiped an estimated $2.5 trillion from the Nasdaq in a single day — and it was driven, above all, by politics.

The KOSPI, South Korea’s benchmark stock index, opened 2.24% lower at 5,263.26 and then fell fast. By 9:03 a.m. local time it had dropped 8.52% to 4,924.61, sliding below the 5,000 mark for the first time in about nine months. The Korea Exchange pulled the emergency brake: a circuit breaker that halted all trading in KOSPI shares, futures and options for 20 minutes.

When trading resumed, the index recovered some ground, climbing back above 5,000. But the selling did not stop. The KOSPI closed the day down 6.02% — a fall of 324.11 points — at 5,059.69, its lowest close since 31 March. At its worst point in the session, the index had touched 4,911.28.

It was the second brutal day in a row. On Thursday, 5 November, the KOSPI had already fallen 5.28% to close at 5,383.80. In two sessions, one of Asia’s biggest stock markets lost more than 11% of its value.

What is the KOSPI — and why does it matter?

The KOSPI, short for Korea Composite Stock Price Index, is the main stock market index of South Korea. It tracks the biggest companies listed on the Korea Exchange in Seoul, much like the FTSE 100 tracks leading shares in London or the S&P 500 does in the United States.

South Korea’s market matters far beyond its own borders because the country makes the memory chips that power the world’s artificial intelligence systems. Samsung Electronics and SK hynix, the two giants of the global memory-chip industry, are both listed in Seoul. When investors worry about the future of AI spending, Korean chip stocks are usually among the first to fall — and on Friday, Samsung and SK hynix led the sell-off.

That is why a bad day in Seoul is read around the world as a warning sign for the whole AI boom.

What is a circuit breaker?

A circuit breaker is an automatic pause button for a stock market. When an index falls too far, too fast, the exchange stops trading for a short time so that panic does not feed on itself.

Under the Korea Exchange’s rules, a first-stage circuit breaker kicks in when the KOSPI stays at least 8% below the previous day’s close for one minute. Trading in shares, futures and options is then suspended for 20 minutes. The idea is simple: give investors time to breathe, check the news and think, rather than selling in a blind rush.

Friday’s halt was one of several circuit breakers triggered on the KOSPI this year — a sign of just how jumpy the market has become. South Korea’s smaller KOSDAQ market also activated a “sidecar”, a five-minute curb on computer-driven programme sell orders, to slow the selling further.

Circuit breakers are not a sign that the market is broken. They are a safety feature, and they worked as designed: the index steadied after the pause and climbed back above 5,000. But the fact that the brake had to be used at all told investors how frightened the market was.

Why did markets fall?

The trigger was politics in the United States. On Tuesday, 3 November, Democrats swept the US midterm elections, winning control of both the House of Representatives and the Senate. Investors quickly concluded that the new Congress would take a much tougher line on artificial intelligence — in particular on the giant data centres that house AI systems.

Democratic candidates across the country had campaigned on slowing the growth of AI data centres, and dozens of local ballot measures sought restrictions on the huge computer facilities. The fear is that tighter rules on data-centre construction, power use and water use could slow the AI building boom that has driven tech shares to record highs.

No new AI law has been passed. Nothing has actually changed yet. But markets move on expectations, and investors decided the political winds had shifted against the AI trade.

The timing mattered too. The election landed on a market that was already nervous about how much money tech companies are spending on AI. Goldman Sachs estimates that AI-related capital spending could reach $7.6 trillion between 2026 and 2031. Research group IDCA counts at least 46 data-centre projects worth $170 billion that have been blocked or stalled by community opposition since January 2024. UBS has estimated that about 30% of the new data centres expected in the next two years could be affected by the election result.

In other words, the market was already asking whether the AI boom was built on solid ground. The midterm result gave that worry a sharp push.

A brutal Thursday on Wall Street

The sell-off began in earnest on Wall Street on Thursday, 5 November. The tech-heavy Nasdaq Composite fell 5.52% — its biggest one-day percentage drop since April 2025 — wiping out an estimated $2.5 trillion in market value, according to Dow Jones data. The S&P 500 fell 4.4%, and the Dow Jones Industrial Average gave back its earlier gains to close down more than 3.4%.

The so-called “Magnificent Seven” — Alphabet, Amazon, Apple, Meta, Microsoft, Nvidia and Tesla — collectively lost around $1 trillion in value in a single trading day, according to the Wall Street Journal and the BBC.

Chipmakers were hit hardest of all. The Philadelphia Semiconductor Index, which tracks the biggest US chip companies, fell more than 12% — its worst day since the depths of the Covid pandemic. Nvidia, the world’s most valuable chipmaker, fell more than 9%, losing over $400 billion in value in a day. AMD and Micron each fell more than 17%, and memory maker SanDisk dropped over 22%.

Every sector of the S&P 500 finished in the red on Thursday. The Nasdaq is now in “correction territory”, having fallen nearly 12% from its record close on 6 October. A correction is the name markets give to a fall of 10% or more from a recent peak.

The sell-off goes global

By Friday morning, the rout had travelled around the world with the sun. Japan’s Nikkei index fell 6%, Taiwan’s stock market suffered its worst week since 2001, and Europe’s main indices fell around 2%.

South Korea took the hardest hit of all, because its market is so heavily loaded with the chip stocks at the centre of the storm. Foreign investors have now sold more than 12 trillion won — about $8.8 billion — of South Korean shares over six trading sessions, according to market reports.

Fear was easy to measure. The KOSPI 200 volatility index, South Korea’s gauge of how nervous investors are, climbed to 64.74, a three-month high. Volatility measures how wildly prices are swinging; when it jumps, it means investors expect more big moves — in either direction.

How South Korea responded

The South Korean government moved quickly. On Friday, Deputy Prime Minister and Finance Minister Lee Hyoung-il chaired an emergency market meeting in Seoul, joined by Financial Services Commission Chairman Lee Eog-weon, Financial Supervisory Service Governor Lee Chan-jin and Bank of Korea Deputy Governor Kwon Min-soo.

The meeting produced one immediate step: from Monday, 9 November, brokerages will be exempt for three months from a rule that requires them to keep collateral worth 140% of the value of margin loans. A margin loan is money an investor borrows from a broker to buy shares; the collateral is the security the broker holds against that loan. When share prices fall sharply, brokers normally force investors to sell — or “liquidate” — their holdings to protect the loan. That forced selling can turn a bad day into a crash.

By suspending the 140% rule for three months, the authorities are giving brokers room to wait instead of forcing sales at the worst moment. Outstanding margin loans stood at 28.64 trillion won on 4 November, down 25.9% from their peak of 38.63 trillion won on 24 June, according to the Korea Financial Investment Association — so the pile of borrowed money at risk is smaller than it was in the summer, but still large.

Officials also said they would prepare further measures if volatility rises, and they described the market’s reaction as excessive given that no AI regulation has actually changed. South Korea’s National Pension Service, one of the world’s biggest pension funds, suspended its sales of domestic shares and even raised its target weighting for them — a vote of confidence, and a buyer of last resort, at a moment when foreign investors were heading for the exit.

The announcement helped. After the emergency measures were revealed, institutional and retail investors turned into net buyers, and the KOSPI clawed its way back above 5,000.

What does this mean for ordinary people?

For most people, a stock market plunge does not change daily life overnight. But it matters in three ways.

First, pensions and savings. Millions of people hold shares indirectly through pension funds and retirement accounts. South Korea’s National Pension Service stepping in to buy is a reminder of how directly ordinary savers’ money is tied to the market’s mood.

Second, jobs and investment. South Korea’s chip industry is the engine of its export economy. If investors lose faith in AI spending, chipmakers may slow investment and hiring, and that ripples through suppliers, towns and families far from Seoul’s trading floors.

Third, confidence. Sharp market falls make banks, businesses and households more cautious. People spend less, companies delay plans, and the whole economy can cool — even if the original trigger was a political result in another country.

That is why governments step in fast when markets fall this sharply. The cost of doing nothing can be much larger than the cost of a three-month rule change.

What happens next

Three things will decide whether Friday was a frightening blip or the start of something bigger.

The first is what the new US Congress actually does. Campaign promises about AI data centres are one thing; laws are another. Investors will watch closely for the first concrete proposals — and for whether the new Congress can even agree on them.

The second is earnings. The AI trade has been built on the belief that huge spending on chips and data centres will pay off. If the big tech companies report strong results and keep spending, the market may decide the sell-off was an overreaction. If they cut back, the fear will deepen.

The third is Monday’s reopening in Seoul. The margin-loan relief takes effect on 9 November, and the market will test whether the government’s measures are enough to steady nerves. Foreign investors, who have sold heavily for six straight sessions, hold the key: if they stop selling, the market can stabilise; if they keep selling, the pressure will continue.

Wall Street steadied somewhat on Friday, with the Nasdaq recovering part of Thursday’s losses. But nobody in Seoul is celebrating yet. The KOSPI is still more than 6% below where it stood on Wednesday, and the questions that caused the panic — how fast AI will grow, and who will be allowed to build it — have not been answered.

Frequently asked questions

What is the KOSPI?

The KOSPI is South Korea’s main stock market index. It tracks the biggest companies listed on the Korea Exchange, including Samsung Electronics and SK hynix, the world’s leading memory-chip makers.

What is a circuit breaker?

An automatic halt in trading. When the KOSPI falls at least 8% below the previous close and stays there for a minute, the Korea Exchange suspends trading in shares, futures and options for 20 minutes to let panic cool.

Why did the KOSPI fall so sharply?

Investors fear that the Democrats’ sweep of the US midterm elections will lead to tighter regulation of artificial intelligence and slower construction of AI data centres. That hit chip stocks hardest, and South Korea’s market is full of them.

How much money was wiped out?

The Nasdaq lost an estimated $2.5 trillion in market value on Thursday, 5 November, and the Magnificent Seven tech giants lost around $1 trillion in a single day. The KOSPI lost more than 11% across Thursday and Friday.

What did the South Korean government do?

It suspended the 140% collateral rule on margin loans for three months from Monday, 9 November, so brokers are not forced to sell investors’ shares at the worst moment. It also promised further measures if volatility continues.

Conclusion

Friday’s trading halt in Seoul was the loudest alarm yet in a week that has shaken the world’s faith in the AI boom. A political result in Washington wiped trillions from tech shares, sent Asia’s markets tumbling, and forced South Korea to halt trading and rewrite its margin-loan rules within hours.

The speed of the fall is a reminder of how much of the recent market rally was built on a single idea: that spending on artificial intelligence would keep growing, unchecked, forever. That idea is now being questioned — not by a company missing its earnings, but by voters and politicians.

Whether the sell-off becomes a lasting downturn depends on what happens next in Washington, in corporate boardrooms and on trading floors in Seoul on Monday. For now, the market has had its warning. The question is whether anyone will listen.

Sources

• Aju Press, “KOSPI crashes over 8%, forcing 20-min halt”, 6 November 2026: https://www.ajupress.com/view/20261106093332933
• Aju Press, “Seoul tweaks margin loan rule to contain stock selloff”, 6 November 2026: https://www.ajupress.com/view/20261106122823452
• SRN News, “AI data-center stocks slip as Democratic sweep clouds expansion plans”: https://srnnews.com/ai-data-center-stocks-slip-as-democratic-sweep-clouds-expansion-plans/
• Gizmodo, “Tech rout wipes out $2.5 trillion with AI investors anticipating heavier scrutiny”, 6 November 2026: https://gizmodo.com/tech-rout-wipes-out-2-5-trillion-with-ai-investors-anticipating-heavier-scrutiny-2000835986
• ASEAN Now, “Trillions wiped off tech giants as midterm rout jolts AI boom”, 6 November 2026: https://aseannow.com/worldnews/trillions-wiped-off-tech-giants-as-midterm-rout-jolts-ai-boom-r2569/
• Invezz, “KOSPI crash today: why South Korea halted trading after an 8% plunge”, 6 November 2026: https://invezz.com/news/2026/11/06/kospi-crash-trading-halt-november-6/
• The Global Banker, “South Korea suspends its 140% margin loan collateral rule for three months as the KOSPI falls 8.52%”: https://www.theglobalbanker.com/south-korea-suspends-its-140-margin-loan-collateral-rule-for-three-months-as-the-kospi-falls-8-52/

This article is for general information and education only. It is not legal or financial advice.