The KOSPI, which opened higher, turned lower and moved away again from the 7,000 level. Amid the external headwind of a surge in U.S. Government Bonds yields, heavy net selling by institutions and profit-taking poured in, and it closed down 1.55%.
On the 18th, the KOSPI closed at 6,869.83, down 108.11 points (1.55%) from the previous trading day. The index opened at 7,127.77, up 149.83 points (2.15%) from the previous trading day, and, buoyed by expectations for an improvement in the artificial intelligence (AI) semiconductor cycle, surged to as high as the 7,120 level (2.15%) early in the session. It then quickly pared gains, turned lower around noon, and extended losses in a weak trend.
In the main board, individual investors net bought 1.1978 trillion won, but institutions net sold 1.1928 trillion won, putting strong pressure on the index. In particular, among institutions, net selling was concentrated in financial investment with 861.6 billion won. Foreign investors alone net bought more than 500 billion won early in the session, helping lift the index, but they later trimmed purchases, ending with a net buy of 55.5 billion won.
Brokerages cited as reasons for the day's decline the emergence of large-scale profit-taking after a short-term surge, the reemergence of Middle East geopolitical risks following the end of the temporary truce between the United States and Iran, and weaker investor sentiment toward tech stocks due to a jump in U.S. Government Bonds yields.
The previous day, New York stocks ended lower across the three major indexes as West Texas Intermediate (WTI) crude jumped 2.6% amid rising tensions between the United States and Iran and the U.S. 10-year Government Bonds yield climbed to 4.726% per year. The Dow Jones Industrial Average fell 272.63 points (0.51%) from the previous trading day to 53,459.78. The Standard & Poor's (S&P) 500 and the Nasdaq also fell 0.52% and 0.32%, respectively.
Helped by the bullish catalyst of a surge in second-quarter revenue at Anthropic, the developer of the AI chatbot Claude, the Philadelphia Semiconductor Index rose 1.6%, leading early gains in domestic semiconductor stocks at the open, but it appears they could not overcome macro uncertainty and the burden of higher Government Bonds yields.
Kim Seok-hwan, a researcher at Mirae Asset Securities, said, "In a high-rate environment where the U.S. 10-year Government Bonds yield is above 4.7%, the 'equity risk premium,' which reflects the investment appeal of stocks versus bonds, continues to slow," adding, "As rate increases persist, accumulated financial market stress and a turn in foreign flows led the domestic market to reverse lower."
Most top market-cap stocks turned weaker. Samsung Electronics(005930), which had risen more than 3% at the open, finished at 268,500 won, down 2.19% from the previous trading day. Samsung Electro-Mechanics (-7.57%), LG Energy Solution (-5.01%), HD Hyundai Heavy Industries(329180) (-4.02%), Hyundai Motor (-3.97%), and Kia (-3.18%) also posted steep declines.
In contrast, SK hynix(000660) rose 1.03% to close at 1,662,000 won. Samsung Life Insurance (3.16%) and SK(034730) (0.85%) were among a handful of gainers.
The KOSDAQ also closed sharply lower. The KOSDAQ finished at 834.20, down 30.45 points (3.52%) from the previous trading day. After opening at 866.59, up 1.94 points (0.22%) from the previous trading day, the KOSDAQ, like the KOSPI, turned lower and widened losses into the close.
On the KOSDAQ, foreign investors and institutions net sold 22.5 billion won and 416.4 billion won, respectively, dragging the index lower. Individuals alone net bought 454.3 billion won, but it was not enough to stem the decline.
Among top KOSDAQ market-cap stocks, HPSP(403870) (5.57%), FADU (4.27%), EO Technics (2.48%), and Jusung Engineering (0.84%)—some semiconductor equipment and component names—held up relatively well.
By contrast, LigaChem Biosciences (-7.73%), Peptron(087010) (-7.22%), EcoPro (-6.94%), EcoPro BM (-6.51%), Rainbow Robotics (-6.19%), and Alteogen (-5.10%)—battery, biotech, and robotics names—closed lower.