Samsung Electronics and SK hynix ended 5 November about $144 billion lower in combined market value, by our arithmetic on Korea Exchange closing prices, up from about $118 billion at midday. SK hynix closed down 9.5% and Samsung down 7.6% from the 4 November close, and the KOSPI closed down 5.3% at 5,383.80.
Yonhap reported that the Democratic Party’s landslide in the US midterm elections “sparked concerns over tighter regulations on artificial intelligence (AI) investments”. Its closing report mentions one trading curb on the day, the sell-side sidecar at 10:16 a.m.
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 closing prices, Samsung Electronics and SK hynix lost about 192.9 trillion won, or about $143.7 billion, of combined market value on 5 November, about $25.7 billion more than at midday. Yonhap tied the fall to concerns that the new US Congress could tighten regulations on AI data centres.
This follows our midday piece, Samsung, SK Hynix Lose $118B by Midday as KOSPI Slides 4%, which used prices from 12:10 to 12:11 Korea time. The selling continued into the afternoon, and all three hit their lows of the day between 14:57 and 14:59, about half an hour before the 15:30 close.
The KOSPI fell 300.00 points, or 5.28%, to 5,383.80, from 5,683.80. It had been down 4.0% at midday; its low of 5,336.88 at 14:57 was 6.1% below the previous close, by our arithmetic.
SK hynix closed at 1,264,000 won, down 132,000 won, or 9.46%, from 1,396,000 won, after a low of 1,250,000 won. Samsung Electronics closed at 201,500 won, down 16,500 won, or 7.57%, from 218,000 won, after a low of 199,800 won. At midday they had been down 8.4% and 5.7%.
By our arithmetic, SK hynix fell about 1.8 times as far as the index at the close, against about twice as far at midday.
Percentage change from the 4 November close for SK hynix, Samsung Electronics and the KOSPI at midday (12:10 to 12:11 Korea time) and at the 15:30 close on 5 November 2026, from Korea Exchange data on Naver Finance. Midday figures are those in our midday piece.
The Value Lost
Our arithmetic uses the same share counts as the midday piece, implied by Naver Finance’s market value figures: about 5.85 billion Samsung common shares and about 730 million SK hynix shares.
On that basis Samsung lost about 96.5 trillion won of market value and SK hynix about 96.4 trillion won, 192.9 trillion won together. At 1,341.90 won to the dollar, the Hana Bank rate at 15:41 Korea time, that is about $71.9 billion each, or about $143.7 billion combined.
That is about 34.4 trillion won, or about $25.7 billion, more than the midday figure of 158.5 trillion won, so the close figure is about 22% larger. It equals about 8.4% of the two companies’ combined value at the 4 November close, and it is more than the roughly 126.4 trillion won they regained the day before, as we reported in Samsung, SK Hynix Regain $94B From Midterm Results-Day Lows. At the afternoon lows the combined figure was about 213 trillion won.
The Stated Cause
Yonhap’s closing report said the Democrats’ victory “raised concerns that the new Congress that takes control in January could tighten regulations on AI data centers, potentially affecting investment in the sector”.
It said the index opened 1.82% lower and extended losses in the morning, and that the Korea Exchange activated a sell-side sidecar at 10:16 a.m., suspending program trading for KOSPI-listed shares for five minutes.
Who Was Selling
Naver Finance’s investor data, read after the close, showed foreign investors as net sellers of about 3.39 trillion won of KOSPI shares, about $2.5 billion, roughly twice the 1.72 trillion won they had sold by midday. Individuals were net buyers of about 2.27 trillion won and institutions about 0.84 trillion won.
The fall widened through the day: 537 KOSPI stocks closed down and 344 up, against 461 down and 421 up at midday.
Across Asia
Chip-equipment makers also fell in Tokyo. Advantest closed down 14.71% at 29,485 yen and Tokyo Electron down 9.42% at 8,753 yen, according to closing prices on Naver Finance, while the Nikkei 225 closed down 1.79%.
In Taipei, the Taiwan Stock Exchange’s TAIEX closed down 3.20% at 41,574.72, while TSMC closed down 20 New Taiwan dollars, or about 0.9% by our arithmetic, at 2,240.
Hong Kong moved the other way. Bloomberg reported that Hong Kong stocks were “staging a comeback as part of a rotation away from” hardware stocks into Chinese internet platforms, with the Hang Seng Index climbing as much as 3.5% and the Hang Seng Tech Index nearly 6%, led by Alibaba and Tencent. At 14:30 Hong Kong time, before the 16:00 close, the Hang Seng was up 3.46% at 24,747.15, according to Naver Finance.
Go deeper, 5 Nov, 08:50Z: our follow-up, Europe Hits a Record on AI Rotation as SK Hynix Falls 9.5%, sets the Seoul close beside the same day’s Hong Kong close and Europe’s record, with an 8.96-point spread between the Hang Seng and the KOSPI by our arithmetic.
Update, 5 Nov, 08:16Z: the Hong Kong close. The Hang Seng Index closed at 24,798.69, up 879.19 points, or 3.68%, according to Naver Finance’s closing data read after the 16:00 Hong Kong close. At 14:30 Hong Kong time it had been up 3.46%.
The Business Lever
The business lever is demand for AI memory and the equipment that makes it. SK hynix and Samsung sell memory used in AI data centres, and Advantest and Tokyo Electron supply tools and testers to chipmakers. Our midday piece also carries a Meritz Securities note, as relayed on X, that says orders received by memory chipmakers for 2027 and 2028 far exceed their supply capacity; we have not read the note itself.
As we read the session, the selling did not ease after midday: all three hit their lows between 14:57 and 14:59 Korea time, and the close was near those lows.
As we read the investor data, foreign investors roughly doubled their net selling between midday and the close, while Korean individuals kept buying.
As we read the region, chip-equipment and memory names fell hardest, Advantest by 14.71% in Tokyo, while Bloomberg reported Hong Kong rising on a rotation into Chinese internet platforms.
Yonhap, 5 November 2026, closing report
“The Democrats’ victory, dubbed a “blue wave,” raised concerns that the new Congress that takes control in January could tighten regulations on AI data centers, potentially affecting investment in the sector.”
Three Implications
FOR MEMORY MAKERS The close turned a midday loss of about $118 billion into about $144 billion, by our arithmetic, with SK hynix down 9.46% and Samsung 7.57%.
FOR CHIP-EQUIPMENT SUPPLIERS Advantest closed down 14.71% and Tokyo Electron 9.42% in Tokyo, while TSMC closed down about 0.9% in Taipei, by our arithmetic.
FOR US DATA-CENTRE BUILDERS Yonhap ties the Seoul fall to US regulation concerns; we reported data center limits leading 40 of 41 votes, and Microsoft’s capex coming in about $5 billion short, as reported by The Information.
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 5 November close priced the demand side: Yonhap ties the fall to concerns over tighter rules on US AI data centres, where that memory ends up. The analysis predates the election and does not discuss it.
What Is Not Established
Yonhap attributes the fall to regulation concerns after the election; no regulation has been proposed or passed in what we read, and the reports do not say which rules investors expect. Bloomberg describes a rotation in Hong Kong; neither report links the two markets directly, and we do not.
The Hang Seng figure in the main text is intraday; its close is in the update above. Investor flows are Naver Finance’s figures read after the close and may be revised. We read Yonhap’s closing report in full and the opening of Bloomberg’s report, not the full article, and we did not see the Korea Exchange notices themselves.
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SK hynix closed down 9.5%, Samsung 7.6% and the KOSPI 5.3% on 5 November, according to Korea Exchange data, with all three at their lows about half an hour before the close. By our arithmetic the two chipmakers lost about $144 billion of market value, about $26 billion more than at midday, while foreign investors sold about 3.39 trillion won of KOSPI shares.
A note on sourcing. Closing prices, lows, investor flows and the exchange rate are Korea Exchange and Hana Bank data read on Naver Finance after the 15:30 Korea time close on 5 November 2026 (06:43 UTC); investor flows may be revised. Taiwan prices are Taiwan Stock Exchange data; Tokyo closes and the intraday Hang Seng figure were read on Naver Finance. The stated cause and the sidecar are as reported by Yonhap; the Hong Kong description is Bloomberg’s.
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.
