The Korea Exchange halted trading in KOSPI-listed shares for 20 minutes from 9:03 a.m. Korea time on 6 November, Yonhap reported, after the index fell more than 8% from the previous close. At the halt the KOSPI was down 8.55% at 4,923.47, Samsung Electronics down 9.98% and SK hynix down 11.71%, according to Korea Exchange data on Naver Finance.
By our arithmetic, the two chipmakers were about 225.6 trillion won, or about $166 billion, lower in combined market value at the halt than at the 5 November close. Yonhap tied the selling to a tech rout on Wall Street, “triggered by concerns that Democrats’ sweeping victory in the U.S. midterms could slow down the pace of the build out of artificial intelligence (AI) data centers”.
Business Pill · Concentration
A short Business Engineer explainer on concentration: when a few big pieces make up most of a total. It teaches the general idea only and says nothing about Samsung, SK hynix or the KOSPI.
The key insight: By our arithmetic on Korea Exchange data at the 9:03 a.m. Korea time halt, Samsung Electronics and SK hynix were about 225.6 trillion won, or about $166 billion, lower in combined market value than at the 5 November close. Yonhap said it was the tenth time this year that the Korea Exchange had activated a circuit breaker.
Yonhap reported the KOSPI open at 5,263.26, down 120.54 points, at 9:01 a.m. The selling then deepened within minutes: Yonhap’s urgent report on the circuit breaker followed at 9:04 a.m., and its report on the halt said trading was suspended for 20 minutes from 9:03.
Yonhap said it was the tenth time this year that the Korea Exchange had activated a circuit breaker. On 5 November, as we reported in Samsung, SK Hynix Lose $144B as KOSPI Closes Down 5.3%, Yonhap’s closing report mentioned one curb, a sell-side sidecar at 10:16 a.m., and the KOSPI closed down 5.28% at 5,383.80.
At the halt the KOSPI had lost 460.33 points. Korean outlets’ headlines, which we read but whose articles we did not, said the index fell below the 5,000 level.
Percentage change from the previous close for SK hynix, Samsung Electronics and the KOSPI at the 5 November close and at the 9:03 a.m. Korea time halt on 6 November 2026, from Korea Exchange data on Naver Finance. The 6 November figures are at the halt, not a close.
What Was Posted on X
Samsung Electronics is down 11% and SK hynix is down 13.6% in Korean premarket trading.
Posted at 23:43 UTC on 5 November, before the Seoul open, the X account @jukan05 wrote that Samsung Electronics was down 11% and SK hynix 13.6% in Korean premarket trading. The piece uses it only for those premarket figures; at the 9:03 a.m. halt both were down less, according to Korea Exchange data.
The Two Chipmakers
Samsung Electronics traded at 181,400 won at the halt, down 20,100 won from 201,500 won, after opening at 185,000 won and touching a low of 175,300 won. SK hynix traded at 1,116,000 won, down 148,000 won from 1,264,000 won, after opening at 1,172,000 won and touching a low of 1,070,000 won.
By our arithmetic, SK hynix fell about 1.4 times as far as the index at the halt.
Before the open, the X account @jukan05 posted that Samsung was down 11% and SK hynix 13.6% in premarket trading. At the halt both were down less than those premarket figures.
The Value Lost
Our arithmetic uses the share counts implied by Naver Finance’s market value figures, the same basis as our 5 November pieces: about 5.85 billion Samsung common shares and about 730 million SK hynix shares.
On that basis Samsung was about 117.5 trillion won lower and SK hynix about 108.1 trillion won lower than at the 5 November close, 225.6 trillion won together. At 1,356.40 won to the dollar, Naver Finance’s rate at 9:13 a.m., that is about $86.6 billion and $79.7 billion, or about $166 billion combined.
That follows the roughly 192.9 trillion won, or about $143.7 billion, the two lost at the 5 November close, by our arithmetic in that piece. We do not add the two days together because they use different exchange rates.
Who Was Selling
Naver Finance’s investor data at the halt showed foreign investors as net sellers of about 133.7 billion won of KOSPI shares, with individuals and institutions net buyers. These are early figures and may be revised.
As we read the open, the selling came fast: Yonhap reported the open at 9:01 a.m. and the halt from 9:03 a.m.
As we read the two days together, the falls at the halt for both chipmakers and the index were already larger than their 5 November closing falls, though the 6 November figures are not a close.
As we read the flows, foreign investors were net sellers at the halt while individuals and institutions were net buyers.
Yonhap, 6 November 2026, halt report
“The benchmark index came under heavy selling pressure following a tech rout on Wall Street, triggered by concerns that Democrats’ sweeping victory in the U.S. midterms could slow down the pace of the build out of artificial intelligence (AI) data centers.”
Three Implications
FOR MEMORY MAKERS At the halt SK hynix was down 11.71% and Samsung 9.98%, about $166 billion of combined market value by our arithmetic.
FOR THE KOREAN MARKET Yonhap counts this as the tenth time this year that the Korea Exchange has activated a circuit breaker; the index was at 4,923.47 at the halt.
FOR US DATA-CENTRE BUILDERS Yonhap ties the Seoul selling to concerns about the pace of the US data-centre build-out; in US trading on 5 November Micron closed down 17.77% and SanDisk 22.42%.
The analysis says: “HBM growth is outpacing accelerator demand, making memory the rate-limiting factor in the AI scaling equation.”
As we read it, the framework is about supply, and the 6 November open priced the demand side: Yonhap ties the selling to concerns about the pace of the US data-centre build-out, where that memory ends up. The analysis predates the election and does not discuss it.
What Is Not Established
The prices in this piece are those at the halt, about three minutes after the open, not a close; trading was halted for 20 minutes, Yonhap reported, and the levels may change after it resumes. Investor flows are early Naver Finance figures.
Yonhap attributes the fall to concerns about the pace of the US data-centre build-out after the midterms; no US rule on data centres has been passed in what we read. We read Yonhap’s English halt report in full and Korean outlets’ headlines only, and we did not see the Korea Exchange notice itself. The premarket figures are an X post’s, not exchange data.
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The Korea Exchange halted KOSPI trading for 20 minutes from 9:03 a.m. on 6 November after an 8%-plus fall, the tenth time this year it had activated a circuit breaker, according to Yonhap. At the halt Samsung was down 9.98% and SK hynix 11.71%, about $166 billion of combined market value by our arithmetic, a day after the two lost about $144 billion.
A note on sourcing. Prices, opens, lows and investor flows are Korea Exchange data, and the exchange rate is Naver Finance’s market rate, read on Naver Finance between 00:14 and 00:17 UTC on 6 November 2026, as of the 9:03 a.m. Korea time halt; investor flows may be revised. The halt, its timing and the stated cause are as reported by Yonhap. Market value losses and share counts are our arithmetic; Samsung’s share count covers common shares only. We did not contact the companies.
Gennaro Cuofano is a CRO and tech executive who has worked in AI since late 2015, starting with bringing NLP, natural-language generation, voice and chatbot products to the marketing industry. His background is in law and finance: he holds a Master's degree in Law and an International MBA with an emphasis on corporate finance (LUISS Business School and the University of San Diego, 2012), and worked as a financial analyst at a real-estate investment firm in San Diego and as an assistant controller. His work focuses on business model strategy, business engineering and, more broadly, structural analysis: how companies make money, read from their own filings. He created FourWeekMBA and leads research there and at The Business Engineer, his newsletter on AI and business strategy, with over 95,000 subscribers and more than 1,000 published analyses. His writing has also appeared on Entrepreneur (for example, How to Digitize a Family Business in Europe) and HackerNoon. Find him on LinkedIn and Substack. See how we source.
