Institutional investors bought nearly 5 trillion won worth of shares on South Korea's main stock market ahead of the Chuseok holiday, while retail and foreign investors both sold. Their buying concentrated on large-cap chipmakers including Samsung Electronics and SK hynix, drawing attention to whether the rally in those stocks will continue after the holiday.
Institutions net-purchased a combined 4.71 trillion won on the main board over six sessions from Sept. 16 through Sept. 23, the last trading day before the holiday, according to the Korea Exchange on the 26th. Apart from net sales of 129.5 billion won on the 22nd, they were net buyers in all five other sessions. Daily purchases topped 1 trillion won on the 16th (1.23 trillion won), the 18th (1.53 trillion won) and the 21st (1.52 trillion won).
The KOSPI climbed 6.85% over the stretch of institutional buying. The index rose in five of the six sessions, slipping just 0.04% on the 17th, and reclaimed the 7,000 level on a closing basis on the 21st for the first time in seven sessions, holding above that mark until the holiday break. Retail investors, meanwhile, sold a net 10.15 trillion won on the KOSPI, while foreign investors unloaded 3.51 trillion won.
The most aggressively bought stocks were the market's chip leaders. Institutions net-purchased 2.78 trillion won of Samsung Electronics and 692.8 billion won of SK hynix over the period. Samsung Electro-Mechanics ranked third at 543.5 billion won. As funds flowed in, Samsung Electronics and SK hynix jumped 14.89% and 10.18%, respectively, while Samsung Electro-Mechanics surged 14.43%.
Longer-term optimism about the memory market is also lending support. Yuanta Securities Korea said tight supply and demand conditions will persist through 2027 and 2028, raising its earnings estimates for Samsung Electronics next year and lifting its target price to 630,000 won from 530,000 won. The brokerage said supply constraints could last longer than expected as high-bandwidth memory (HBM) production eats into capacity for conventional DRAM and as the spread of artificial intelligence inference drives demand for higher-capacity memory.
Institutional buying was not confined to the chip supply chain. Doosan ranked fourth with 147 billion won, followed by KB Financial Group (127.5 billion won), SK Square (113.4 billion won) and Hanmi Pharmaceutical (93.2 billion won). Doosan and SK Square rose 17.30% and 19.00%, respectively, helped by news including Doosan's capacity expansion for copper-clad laminates (CCL) used in AI data centers, SK Square's share cancellation, and expectations of higher stake value on SK hynix's share strength. LG Electronics (75 billion won), Samsung Electronics preferred shares (73.6 billion won) and Korean Air (67.4 billion won) also ranked among the top net purchases.
The stock institutions sold most heavily was NAVER. Its shares tumbled 5.49% over the six sessions as institutions net-sold 195.5 billion won. Selling was also concentrated in Doosan Enerbility (128.1 billion won), Samsung SDI (57.6 billion won) and GS (54.3 billion won).
After the holiday, a series of events that will gauge the health of the chip market are due, including Micron's earnings, September export data and Samsung Electronics' preliminary results. "Trading value fell sharply ahead of the holiday, so rather than reading much into this week's swings, investors need to focus on issues after Chuseok," said Kang Jin-hyuk, an analyst at Shinhan Securities. "With semiconductor momentum carrying forward in relay fashion, solid fundamentals could justify the recent compressed gains."
