In the South Korean market’s regular session (09:00–15:30) on August 19, 2026, the KOSPI fell 398.66 points (-5.80%) to 6,471.17 points, while the KOSDAQ declined 9.74 points (-1.17%) to 824.46 points. All four tracked stocks were weaker, with SK Square and SK hynix declining by double digits and in the 9% range, respectively—more than the index decline.

KOSPI Closes at 6,471.17 Points, With a Larger Decline Than the KOSDAQ

Index August 19, 2026 Regular-Session Close August 19, 2026 Change
KOSPI 6,471.17 points -398.66 points (-5.80%)
KOSDAQ 824.46 points -9.74 points (-1.17%)

The KOSPI opened at 6,528.77 points in the regular session on August 19, 2026, rose as high as 6,614.39 points, fell as low as 6,400.81 points, and closed at 6,471.17 points. KOSPI closing data

The KOSDAQ opened at 810.08 points on the same trading day, moved between 840.50 points and 804.02 points, and ended the regular session at 824.46 points. KOSDAQ closing data

The editorial interpretation based solely on closing data is that both indexes declined, but the KOSPI’s percentage loss on August 19, 2026, was larger than that of the KOSDAQ. The relationship among the open, high, low, and close shows only the price range within that day’s regular session; it does not establish a causal relationship showing that a particular investor group or external factor caused the decline.

SK Square Falls -11.54% and SK hynix -9.75%, Extending Losses

SK Square closed the regular session on August 19, 2026, at 1,004,000 won, down 131,000 won (-11.54%) from the previous trading day. It opened at 1,071,000 won, reached a high of 1,111,000 won, fell to a low of 993,000 won, and recorded regular-session volume of 1,084,250 shares. SK Square closing data Past analysis is available at the SK Square stock hub.

SK hynix closed at 1,500,000 won on August 19, 2026, down 162,000 won (-9.75%) from the previous trading day. It traded between an open of 1,552,000 won, a high of 1,628,000 won, and a low of 1,486,000 won, with regular-session volume of 7,819,629 shares. SK hynix closing data Previous analysis is available at the SK hynix stock hub.

Collected pre-market articles cited sharp declines in U.S. semiconductor stocks and interest rates as key factors to watch. This is the market interpretation presented in the original articles and cannot be conclusively identified as the cause of the August 19, 2026 declines in SK hynix or SK Square based on domestic closing data alone. Original pre-market U.S. market article Original report on the New York market

Samsung Electronics and Hyundai Motor Also Decline Together

Samsung Electronics ended the regular session on August 19, 2026, at 247,500 won, down 21,000 won (-7.82%) from the previous trading day. It opened at 257,500 won, reached a high of 258,000 won, fell to a low of 246,500 won, and recorded regular-session volume of 38,359,205 shares. Samsung Electronics closing data Historical analysis of the company is available at the Samsung Electronics stock hub.

Hyundai Motor closed at 414,000 won on the same trading day, down 21,000 won (-4.83%) from the previous trading day. It traded between an open of 423,500 won, a high of 425,000 won, and a low of 406,500 won, with regular-session volume of 876,539 shares. Hyundai Motor closing data Previous records are available at the Hyundai Motor stock hub.

The editorial interpretation is that all tracked stocks fell on August 19, 2026, and that SK Square, SK hynix, and Samsung Electronics declined more sharply than Hyundai Motor. However, this relative performance is a comparison of simultaneous movements in closing prices and is not evidence for conclusively attributing the moves to sector- or company-specific news or trading flows.

Investor-Flow Data and Reported Explanations Should Be Viewed Separately

In investor-flow data for August 19, 2026, retail investors were net buyers of 46,358억원, foreign investors were net sellers of 34,884억원, and institutions were net sellers of 13,232억원. Investor-flow data by investor type for August 19, 2026 Retail net buying and foreign and institutional net selling occurred alongside the index decline on the same trading day, but this coincidence alone cannot conclusively establish that any one group’s trading directly caused the index movement.

Yonhap News cited negative developments from the United States as the backdrop for the KOSPI’s reversal lower, and cited institutional net selling in its explanation of trading flows. SBS Biz likewise cited weakening foreign net buying and institutional selling as the backdrop for the decline. These are interpretations presented in the respective articles and should be read separately from the regular-session closing prices and investor-flow data in this article. Original Yonhap News article Original SBS Biz article

Three Items to Check in the Next Regular Session

  • For the KOSPI, the next regular-session closing trend should be checked against the August 19, 2026 regular-session close of 6,471.17 points and that day’s low of 6,400.81 points. For the KOSDAQ, it should be checked against the close of 824.46 points and that day’s low of 804.02 points.

  • It should be observed how the relative changes of SK Square at -11.54%, SK hynix at -9.75%, Samsung Electronics at -7.82%, and Hyundai Motor at -4.83% on August 19, 2026, change in the next regular session. This is an item to check only and is not a basis for determining future direction.

  • It should be checked whether the direction of investor flows—retail net buying of 46,358억원, foreign net selling of 34,884억원, and institutional net selling of 13,232억원 on August 19, 2026—changes in the next regular-session data. Investor flows and prices are items to observe together, but causality cannot be conclusively established from figures for a single trading day alone.