The KOSPI index, which was at 4,200 points at the end of last year, surpassed 5,800 points and set a record high day after day, but a small number of stocks were found to have led the index's rise. On the back of the "semiconductor super cycle (boom)," Samsung Electronics and SK hynix shares soared, pushing the two corporations' share of KOSPI market capitalization to nearly 40%.
As of the 20th, the market capitalizations of Samsung Electronics and SK hynix were 1,125 trillion won and 690 trillion won, respectively, with the combined market cap of the two stocks accounting for 37.8% (1,816 trillion won) of the total. That is the highest level on record. Including preferred shares, the two stocks account for more than 40% (1,926 trillion won) of the Korea Exchange main board's market capitalization.
Until recently, the two stocks' combined market-cap weight moved in the high-20% to low-30% range. In March 2020, during a semiconductor upcycle, the two stocks made up 31.2% of the total market cap, but the share has risen sharply of late.
Over the past six months (Aug. 20, 2025–Feb. 20, 2026), the KOSPI index jumped 84.3%, from 3,151.56 to 5,808.53. During this period, KOSPI market capitalization rose from 2,574.972 trillion won to 4,803.601 trillion won, an increase of 2,228.629 trillion won.
Of that, the increases in the market caps of Samsung Electronics (70.7989 trillion won) and SK hynix (50.487 trillion won) accounted for 54.4%, more than half. Effectively, the two stocks drove the KOSPI's rise.
With demand for artificial intelligence (AI) chips surging, expectations that the two corporations' earnings will improve sharply have fueled the share-price rally. According to securities-house consensus (average estimates), Samsung Electronics' revenue and operating profit this year are expected to be 487.9577 trillion won and 167.5617 trillion won, up 46% and 284% from a year earlier. SK hynix's revenue and operating profit are forecast at 211.6896 trillion won and 143.4868 trillion won, jumping 118% and 204% from a year earlier.
On the flows side, retail money inflows stand out. Funds have poured in, mainly into leveraged and semiconductor exchange-traded funds (ETFs), adding momentum to the rally.
During the same period, the top net buyer of Samsung Electronics was the financial investment category, which reflects retail ETF money, totaling 7.417 trillion won. For SK hynix as well, the financial investment category was largest at 9.2264 trillion won. Foreign investors were net buyers of Samsung Electronics to the tune of 972 billion won in the period, but they were net sellers of SK hynix totaling 16.047 trillion won.
Kim Rok-ho, an analyst at Hana Securities, said, "There is a possibility that memory prices will be revised up further in the first quarter as well as the second, so there is still room for upward earnings revisions." Kim added, "Although the stock gains since the start of the year are a burden, considering fundamentals such as industry conditions and memory prices and the limited supply situation, there is still no clear basis to support a share-price decline."
However, as concentration in the semiconductor sector has intensified, the neglect of small and mid-cap stocks has become more pronounced. The KOSPI is on the verge of a new milestone at the 6,000 level, but investors who did not buy Samsung Electronics and SK hynix are likely not feeling the recent bull market.
Still, since semiconductors are a representative cyclical industry, if a correction in memory prices or a slowdown in the pace of AI investment materializes, index volatility could increase further.
Even so, the securities industry expects the semiconductor super cycle to continue for the time being. Kang Dae-seung, an analyst at SK Securities, said, "In the flow of a 'K-shaped economy,' a growth structure centered on export corporations is being maintained," adding, "As private and government funds are likely to concentrate on AI investment, a semiconductor-corporation-led share rally could continue even after first-quarter earnings are released."