In South Korea’s regular market session (09:00–15:30) on September 11, 2026, the KOSPI and KOSDAQ both closed lower at 6,909.91 points and 820.64 points, respectively. All four tracked stocks also declined, with SK Square and Samsung Electronics recording closing declines larger than those of both indices.

Index September 11, 2026 regular-session close Change from previous trading day September 11, 2026 regular-session high·low
KOSPI 6,909.91 points -124.01 points(-1.76%) 6,948.83 points·6,802.50 points
KOSDAQ 820.64 points -16.28 points(-1.95%) 826.53 points·816.91 points

KOSPI Falls Back to the 6,900 Level, While KOSDAQ Posts a Larger Decline

The KOSPI opened at 6,802.50 points in the regular session on September 11, 2026, rose as high as 6,948.83 points intraday, and closed at 6,909.91 points. It was down -124.01 points(-1.76%) from the previous trading day, with its opening level and intraday low both at 6,802.50 points. KOSPI closing data

The KOSDAQ opened at 816.91 points on the same day, September 11, 2026, reached an intraday high of 826.53 points and an intraday low of 816.91 points, and finished the regular session at 820.64 points. It fell -16.28 points(-1.95%) from the previous trading day, a decline 0.19 percentage points larger than the KOSPI’s -1.76%. The simultaneous decline in both indices and the difference in their closing percentage changes can be confirmed, but price movements alone cannot identify sector-specific fund flows or the cause of the declines. KOSDAQ closing data

SK Square -4.05% and Samsung Electronics -3.53%, Underperforming the Indices

SK Square closed at 1,089,000 won on September 11, 2026, down 46,000 won(-4.05%) from the previous trading day. Its opening price and intraday high were both 1,111,000 won, its intraday low was 1,066,000 won, and trading volume was 519,128 shares. It posted the largest closing percentage decline among the tracked stocks, exceeding both the KOSPI’s -1.76% and the KOSDAQ’s -1.95%. However, this relative decline alone cannot establish the reasons behind price movements in its holdings or in a particular sector. SK Square closing data and the SK Square stock hub provide access to prior analysis.

Samsung Electronics fell 9,500 won(-3.53%) to 259,500 won on September 11, 2026. It recorded an opening price of 260,000 won, an intraday high of 264,000 won, an intraday low of 256,500 won, and trading volume of 20,647,923 shares. Its closing percentage decline was larger than both the KOSPI’s -1.76% and the KOSDAQ’s -1.95%. Samsung Electronics closing data and the Samsung Electronics stock hub provide related records.

SK hynix fell 41,000 won(-2.21%) to 1,812,000 won on September 11, 2026. It recorded an opening price of 1,800,000 won, an intraday high of 1,827,000 won, an intraday low of 1,768,000 won, and trading volume of 3,879,183 shares. Its decline was larger than that of the KOSPI but 0.26 percentage points smaller than that of the KOSDAQ. SK hynix closing data and the SK hynix stock hub are available for reference.

Hyundai Motor closed at 382,500 won on September 11, 2026, down 6,500 won(-1.67%). It recorded an opening price of 382,500 won, an intraday high of 385,000 won, an intraday low of 378,000 won, and trading volume of 658,207 shares. It posted the smallest decline among the tracked stocks, with a percentage decline 0.09 percentage points smaller than the KOSPI’s -1.76%. Hyundai Motor closing data and the Hyundai Motor stock hub provide access to prior analysis.

Investor Flow Figures and Market Reports Are Different Types of Information

Investor net trading totals on September 11, 2026 were +18,680 hundred-million won for retail investors, -22,915 hundred-million won for foreign investors, and -12,258 hundred-million won for institutions. Retail investors were recorded as net buyers, while foreign investors and institutions were recorded as net sellers. These flow figures can be reviewed alongside the same-day KOSPI decline of -124.01 points(-1.76%) and KOSDAQ decline of -16.28 points(-1.95%), but their occurrence on the same day alone does not establish that trading by any one group directly caused the index declines. September 11, 2026 investor flow data

A Yonhap News intraday market report on September 11, 2026 cited international oil prices and other factors as reasons for the decline, and referred to retail net buying and foreign and institutional net selling as intraday investor flows at the time. This is the interpretation and intraday situation presented by the report; it should not be combined with the 15:30 regular-session closing investor-flow totals or read as a conclusive cause of the closing decline. Yonhap News intraday market report

A separate market report on the same day cited pressure from oil prices and interest rates, along with the potential for volatility related to the simultaneous expiration of futures and options and KRX Semiconductor Index rebalancing. This is the market interpretation in the original article. The day’s closing data do not include interest-rate or oil-price figures, so closing data alone cannot measure the extent to which those factors affected the actual decline. Yonhap News market report

Three Items to Review in the Next Regular Session

  • The KOSPI’s September 11, 2026 closing level of 6,909.91 points and intraday high·low of 6,948.83 points·6,802.50 points, and the KOSDAQ’s closing level of 820.64 points and intraday high·low of 826.53 points·816.91 points, can be compared with figures from the next regular session. KOSPI data and KOSDAQ data

  • For the tracked stocks, the closing percentage changes of SK Square -4.05%, Samsung Electronics -3.53%, SK hynix -2.21%, and Hyundai Motor -1.67% on September 11, 2026 can be reviewed for how they differ from the indices in the next regular session.

  • Investor net trading figures of +18,680 hundred-million won for retail investors, -22,915 hundred-million won for foreign investors, and -12,258 hundred-million won for institutions on September 11, 2026 can be compared with totals from the next regular session. Prices and investor flows should be reviewed together, while avoiding conclusions of causality based solely on simultaneous changes during a single trading day. Investor flow data