[Edaily Reporter PARK MIN ] On the 12th, the KOSPI plunged more than 3% during the trading session to the 6,400 level, driven by a simultaneous decline in SamsungElectronics(005930)and SK hynix(000660). The index is facing strong downward pressure due to a combination of macroeconomic headwinds—such as international oil prices surpassing $100 and a sharp rise in U.S. Treasury yields—and concerns over a supply-demand gap as Samsung Electronics’ share buyback program, which has been propping up the market, nears its conclusion.

According to MP Doctor, as of 1:32 p.m. today, the KOSPI is trading at 6,444.46, down 181.47 points (2.74%) from the previous trading day. The index opened at 6,578.17, down 47.76 points (0.72%) from the previous close, and has since extended its losses, dipping as low as 6,416.19 during the session. This marks the fourth consecutive trading day of declines.

By investor type, foreign investors are leading the decline, continuing their selling streak for the fifth consecutive trading day. As of now, foreign investors alone have recorded net sales of 1.317 trillion won. Meanwhile, retail investors are absorbing the selling pressure with net purchases of 732.2 billion won, and institutional investors with 93.6 billion won; however, these efforts appear insufficient to counter the fierce selling pressure from foreign investors.

At the same time, the KOSDAQ Index is also plummeting, down 34.51 points (3.87%) from the previous trading day to 857.76. In the KOSDAQ market, foreign investors and institutions are driving the index down with net sales of 91.3 billion won and 125.2 billion won, respectively, while only retail investors are making net purchases of 221.0 billion won. The number of declining stocks reached 1,464, overwhelming the number of advancing stocks (216).

Among the top-volume stocks on the KOSPI, major semiconductor stocks—whose share buyback programs are nearing completion—have all turned bearish, dragging down the index.

SK hynix(000660)is trading at 1,626,000 won, down 3.27% from the previous trading day, while SamsungElectronics(005930)is also down 3.44% at 253,000 won. Related stocks such as SamsungElectronics(1P)(005935)(-1.86%), SamsungElectroMechanics(009150)(-2.46%), and SKSQUARE(402340)(-4.48%) also fell sharply across the board.

In particular, LG Innotek(011070), whose operating profit forecast was lowered due to the weakening won-dollar exchange rate, plummeted 13.90%, while LGELECTRONICS(066570)(-6.68%) extended its losses. In contrast, KUMHOE&C(002990)(23.43%) continued its sharp rise due to specific company news, and some secondary battery stocks, such as LG Energy Solution(373220)(1.12%) and SAMSUNG SDI CO.,LTD.(006400)(0.53%), managed to hold steady.

Among the top-traded stocks on the KOSDAQ, panic selling continued, particularly in technology growth stocks such as semiconductor materials, parts, and equipment, as well as robotics. ROBOTIS(108490)is trading at 262,000 won, down 11.93%, while LEENO Industrial Inc(058470)(-10.35%), SIMMTECH Co., Ltd.(222800)(-7.93%), TAIHAN Fiberoptics Co.,LTD(010170)(-6.07%), JUSUNG ENGINEERING Co.,Ltd.(036930)(-5.61%), and WONIK IPS Co.,Ltd.(240810)(-2.47%) all saw sharp declines.

The securities industry points to growing concerns over a “supply-demand cliff” as the primary factor behind this week’s decline, as the share buybacks by SamsungElectronics and SK hynix—which totaled 55 trillion won—have effectively reached their final stages.

In addition, analysts note that macroeconomic headwinds are exerting strong downward pressure on the market, as geopolitical risks in the Middle East—including the possibility of U.S. military intervention following the attack on Riyadh Airport in Saudi Arabia—have resurfaced, pushing international oil prices above $100 per barrel and causing the yield on the 10-year U.S. Treasury note to breach 5.3% during the trading session.

In particular, the fact that semiconductor stocks continued to underperform relative to the broader market—even as all three major U.S. stock indices in New York rose on the 9th (local time)—also weighed on the domestic stock market. Amid concerns over a slowdown in demand following memory price hikes, shares of memory companies such as Micron (-0.66%), SanDisk (-1.72%), and SK hynix American Depositary Receipts (ADRs) (-0.86%) fell, and the Philadelphia Semiconductor Index dropped 0.41%.

This was driven by foreign media reports stating that AI company OpenAI’s annualized revenue as of the end of last month stood at $50 billion—below market expectations ($68 billion to $70 billion)—which amplified doubts about AI profitability. Although it was later revealed that OpenAI’s revenue had not actually decreased but was merely the result of a difference in accounting methods, this failed to restore the sharply weakened investor sentiment.

Industry experts advise that a conservative approach is necessary until it is confirmed that foreign investors are returning to the market and international oil prices have stabilized, as uncertainty regarding the interest rate path could widen again depending on the results of the U.S. Consumer Price Index (CPI) and Producer Price Index (PPI) for September, which are set to be released later this week.

Han Ji-young, an analyst at KIWOOM Securities, said, “It is undeniable that market concerns surrounding the ‘super cycle’ narrative for semiconductors—the market’s leading sector—as well as issues regarding earnings visibility and sustainability beyond 2027, have not been fully resolved.” She added, “We have reached a point where it is crucial to assess how much next year’s earnings estimates for SamsungElectronics and SK hynix can be revised upward, and the extent to which this will drive upward revisions in earnings estimates for the KOSPI as a whole.”