The Korea Composite Stock Price Index (KOSPI) extended a "record-high rally" for a fourth straight trading day. As semiconductor shares stayed strong on the government's policy reversal to keep the 5 billion won threshold for large shareholders' capital gains tax, the index topped 3,400 for the first time in 42 years and eight months since January 1983, when the KOSPI began using a market-cap-weighted methodology. It briefly rose above 3,420 intraday.
On the 15th, the KOSPI closed at 3,407.31, up 11.77 points (0.35%) from the previous transaction day. It broke through 3,400 with 10 straight trading days of gains since the 2nd. In particular, the index set closing record highs for four consecutive days, following 3,314.53 on the 10th, 3,344.20 on the 11th, and 3,395.54 on the 12th, through this day.
The KOSPI opened at 3,407.78, up 12.24 points (0.36%) from the previous session, piercing the 3,400 mark at the opening. In early trading, supported by retail buying, it climbed as high as 3,420.23. It then pared gains, slipping below 3,400 to 3,391.33, but rebounded in the afternoon.
Foreign investors led the rise with a sixth straight "Buy Korea," net buying 139.6 billion won. Individuals, who had sold for nine consecutive trading days through the 12th after starting with 347.4 billion won in net sales on the 2nd, net bought 75 billion won on the day. Institutions took profits, net selling 201 billion won.
Expectations for U.S. rate cuts and the government's announcement that it would keep the capital gains tax threshold for large shareholders boosted the rally. Earlier in the morning, Vice Prime Minister and Minister of Economy and Finance Koo Yoon-cheol said at the National Assembly, "To vitalize the capital market, we decided to maintain the large shareholder threshold at the current 5 billion won."
Koo also sought to ease policy doubts by delivering a keynote speech at "Korea Investment Week (KIW) 2025," held at the Conrad Hotel in Yeouido-dong, Seoul. He emphasized, "We will go all-in on artificial intelligence (AI) and the 30 tasks of the super-innovation economy to take the KOSPI to 5,000 and beyond, no matter what."
By stock, holding companies and securities shares were strong. As expectations grew for a lower separate tax rate on dividends following the confirmation to keep the large shareholder capital gains tax threshold at 5 billion won, Samsung C&T, which serves as the Samsung Group's holding company, jumped more than 7%. Shares of Mirae Asset Securities and Hana Financial Group also rose.
Semiconductor shares stayed strong on the day. Despite U.S.-origin tariff effects, information and communications technology (ICT) exports in August hit a record high, confirming strong demand driven by data centers. In particular, shares of Samsung Electronics and SK hynix, the KOSPI's two top semiconductor names, rose and pulled the index higher.
Hyundai Motor and Kia fell more than 3%. Unlike Japan, which will face a 15% tariff starting on the 16th, uncertainty over U.S. tariffs on domestically produced cars continues. Nuclear power and shipbuilding names such as Doosan Enerbility and Hanwha Ocean, which had been strong around the Korea-U.S. summit, also declined.
Lee Kyung-min, a researcher at DAISHIN SECURITIES, said, "While holding companies and securities shares, which had been policy losers to semiconductor stocks, rose, the previous leaders fell," adding, "At the 3,400 level, psychological resistance and profit-taking pressure increased, and share prices of previous leaders such as nuclear power generation, shipbuilding, and K-culture declined."
The KOSDAQ also finished higher. It closed at 852.69, up 5.61 points (0.66%) from the previous transaction day. It opened at 849.64, up 2.56 points (0.30%) from the prior session, and climbed to as high as 852.32 intraday. Despite foreign and institutional "sell" flows, individuals net bought 211.1 billion won, lifting the index.
Among top market-cap names, performance was mixed. Secondary battery shares such as ECOPRO BM and Ecopro and robot shares such as Rainbow Robotics rose, while bio stocks including Peptron, PharmaResearch, ABL Bio, and LigaChem Biosciences fell.
Lee Jae-won, a researcher at Shinhan Investment & Securities, said, "Share prices of secondary battery and robot names reacted to the government's all-in will for the super-innovation economy and President Lee Jae-myung's mention of abolishing new industry regulations at the regulatory rationalization strategy meeting," adding, "On expectations for a recovery in the semiconductor cycle, SIMMTECH and Tes also rose."
Meanwhile, in the Seoul foreign exchange market, the won-dollar exchange rate was 1,388.40 as of 4 p.m., down 7 won (0.5%) from the previous transaction day.