[Edaily Reporter Kim Kyung-eun ] The KOSPI, which had plummeted more than 5% during the session, narrowed its losses toward the close and ended trading around the 5,730 level. Concerns over the profitability of artificial intelligence (AI) investments spread following earnings reports from major U.S. tech companies, triggering a wave of selling centered on large-cap semiconductor stocks such as SamsungElectronics and SK hynix. With foreign investors net selling over 1.6 trillion won, a sell-side circuit breaker was even triggered due to a sharp intraday drop in KOSPI 200 futures prices.

According to MP Doctor on the 30th, the KOSPI closed at 5,730.74, down 206.92 points (3.48%) from the previous trading day. The index opened at 5,760.35, down 177.31 points (2.99%) from the previous session, and fell as low as 5,599.42 during the session. The intraday decline reached 5.70%.

At 10:04:55 a.m. that day, a sell-side sidecar was triggered in the KOSPI market. This marks the second trading day since the buy-side sidecar was triggered on the 28th, and it is the 28th time a sidecar has been triggered in the KOSPI market this year. The sell-side sidecar is a mechanism that suspends the effectiveness of program sell orders for five minutes if the KOSPI 200 futures price remains down by 5% or more compared to the previous trading day for more than one minute.

In the afternoon, buying pressure from institutional and retail investors helped partially recover the losses. Foreign investors led the index lower that day with net sales of 1.6231 trillion won. Institutional and retail investors posted net purchases of 741.3 billion won and 628.0 billion won, respectively.

The domestic stock market was dragged down by a series of disappointing earnings reports from U.S. Big Tech companies. Following Alphabet, earnings reports from Amazon and Intel also highlighted profitability pressures stemming from expanded AI investments, causing selling pressure to spread across the entire semiconductor sector.

Lee Kyung-min, an analyst at DaishinSecurities, explained, “The successive earnings announcements from Alphabet, Intel, and Amazon have heightened doubts about the sustainability and profitability of AI investments,” adding, “Investor sentiment toward AI and semiconductors has weakened as both poor earnings outlooks and the burden of massive capital expenditures have come to the fore simultaneously.”

Among the top market-cap stocks, semiconductor shares saw particularly sharp declines. SamsungElectronics(005930)closed at 225,000 won, down 7,000 won (3.02%) from the previous trading day. SK hynix(000660)closed at 1,418,000 won, down 108,000 won (7.08%). SKSQUARE(402340)(-5.88%) and SamsungElectroMechanics(009150)(-7.50%) also fell sharply.

Selling pressure was seen not only in AI-related stocks but also in the automotive and defense sectors. KIA CORPORATION(000270)plummeted 11.73%, while HANWHA AEROSPACE(012450)(-8.42%) and HYUNDAI ROTEM(064350)(-3.59%) also fell. In contrast, SAMSUNG BIOLOGICS(207940)(8.86%), Celltrion(068270)(1.22%), and SAMSUNG SDI CO.,LTD.(006400)(0.93%) rose.

By sector, medical and precision instruments plunged 7.13%, recording the largest decline. Construction (-6.22%), transportation equipment and parts (-4.88%), electrical and electronics (-4.67%), and machinery and equipment (-4.01%) also showed weakness. In contrast, pharmaceuticals (4.90%), textiles and apparel (1.04%), and transportation and warehousing (1.33%) rose.

The KOSDAQ index closed at 724.38, down 28.85 points (3.83%) from the previous trading day. The index opened at 737.76, fell to 717.27 during the session, and then partially recovered.

In the KOSDAQ market, foreign and institutional investors recorded net sales of 26.7 billion won and 137.5 billion won, respectively. Retail investors recorded net purchases of 168.7 billion won.

Among the top-market-cap stocks, Alteogen Inc.(196170)(-4.09%), ECOPRO CO., LTD(086520)(-1.50%), ECOPRO BM CO., LTD.(247540)(-1.30%), JUSUNG ENGINEERING Co.,Ltd.(036930)(-6.78%), Rainbow Robotics(277810)(-3.84%), EO Technics Co., Ltd.(039030)(-6.99%), and SIMMTECH Co., Ltd.(222800)(-8.10%) all fell across the board.