[Edaily Reporter Shin Ha-yeon ] The KOSPI and KOSDAQ plunged by around 6% in early trading on the 15th, triggering a series of sell-side circuit breakers in both major markets. Overnight, the U.S. September Consumer Price Index (CPI) came in stronger than market expectations, heightening concerns over further interest rate hikes by the Federal Reserve (Fed). The fallout from the sharp decline in tech and artificial intelligence (AI)-related stocks on the New York Stock Exchange appears to be spilling over into the domestic stock market.

According to MP Doctor on the 15th, as of 9:22 a.m. that day, the KOSPI was trading at 5,649.31, down 359.50 points (5.98%) from the previous trading day. The index opened at 5,673.01, fell to 5,615.72 during the session, and reached an intraday high of 5,751.45.

Due to the sharp decline in the index, the KOSPI sell-side car was triggered during the trading session. The KOSPI sell-side car is a mechanism that temporarily suspends the effectiveness of program sell orders when the KOSPI 200 futures price remains more than 5% below the benchmark price for at least one minute.

Overnight, U.S. stock markets fell across the board as September inflation data came in stronger than expected. On the 14th (local time), the Dow Jones Industrial Average fell 0.09%, the S&P 500 closed down 1.11%, and the tech-heavy Nasdaq Composite Index closed down 1.88%.

U.S. CPI for September rose 0.6% month-over-month and 3.7% year-over-year. In particular, core CPI—excluding food and energy—rose 0.3% month-over-month, exceeding market expectations of 0.2%, which heightened concerns about inflation. In the interest rate futures market, the likelihood of a benchmark rate hike by the Federal Open Market Committee (FOMC) this month rose rapidly following the CPI announcement.

The pressure from rising interest rates hit AI and semiconductor-related stocks particularly hard. AI infrastructure stocks such as Oracle, CoreWeave, and Navius plummeted, and the Philadelphia Semiconductor Index also fell sharply. Concerns that prolonged high interest rates could lead to burdens from large-scale data center investments and borrowing costs are believed to have dampened investor sentiment across the tech sector.

Han Ji-young, an analyst at KIWOOM Securities, commented on the day’s stock market, stating, “The market is expected to open lower due to the ripple effects of a simultaneous plunge in U.S. AI infrastructure stocks—which are exposed to profitability concerns amid macroeconomic headwinds, such as the U.S. September CPI exceeding consensus estimates.” However, she added, “Assuming a lower opening today, there is a possibility of technical buying following seven consecutive trading days of sharp declines, and the market is expected to narrow its losses as it digests
the market is expected to digest the TSCM earnings announcement and narrow the losses.”

He further noted, “The fact that the KOSPI extended its losing streak to six consecutive trading days yesterday—with an intraday rebound failing to materialize—is a factor that undermines market confidence in a future rebound,” adding, “This demonstrates that simply relying on the perception of an oversold market or bargain-hunting based on attractive valuations has its limits in quickly reversing the index’s downward trend.”

In terms of supply and demand, foreign investors are net sellers of 698 billion won on the stock market. In contrast, institutional investors are net buyers of 647.7 billion won, while retail investors are net buyers of 8.9 billion won. Program trading shows a net buying position of 904 billion won, comprising 476.1 billion won in arbitrage trading and 427.9 billion won in non-arbitrage trading.

Top-market-cap stocks are all trading lower. SamsungElectronics(005930)is trading at 216,500 won, down 6.68% from the previous trading day. SK hynix(000660)is trading at 1,300,000 won, down 8.39%. In addition, SamsungElectronics(1P)(005935)(-5.18%), SKSQUARE(402340)(-7.75%), LG Energy Solution(373220)(-3.67%), SamsungElectroMechanics(009150)(-9.97%), HyundaiMotor(005380)(-4.31%), and KB Financial Group(105560)(-1.57%) are all trading lower.

By sector, healthcare and precision instruments, as well as electrical and electronics, are down by around 8%, and most other sectors—including machinery and equipment, manufacturing, construction, securities, distribution, finance, chemicals, metals, IT services, electricity and gas, textiles and apparel, insurance, general services, non-metals, telecommunications, and paper and wood—are also trading lower.

At the same time, the KOSDAQ index is trading at 769.50, down 54.38 points (6.60%) from the previous trading day. The index opened at 784.45 today and fell as low as 766.94 during the session. In terms of supply and demand, foreign and institutional investors are net buyers of 47.3 billion won and 12.3 billion won, respectively, while retail investors are net sellers of 57.9 billion won. Program trading shows a net buying position of 119.2 billion won.

Among the top market-cap stocks, Alteogen Inc.(196170)(-4.68%), ECOPRO CO., LTD(086520)(--8.41%), ECOPRO BM CO., LTD.(247540)(-8.67%), JUSUNG ENGINEERING Co.,Ltd.(036930)(-13.31%), Rainbow Robotics(277810)(-7.60%), HLB INC.(028300)(-2.98%), LEENO Industrial Inc(058470)(-7.63%), EO Technics Co., Ltd.(039030)(-7.79%), and WONIK IPS Co.,Ltd.(240810)(-12.10%) are all showing sharp declines.