In the first half of this year, the KOSPI, led by Samsung Electronics and SK hynix, set a record high, while the KOSDAQ fell by nearly 80%, deepening a so-called "K-shaped polarization." The slump in bio and healthcare stocks was particularly pronounced on the KOSDAQ.
According to the Korea Exchange (KRX) on the 29th, in the first half of this year (Jan. 2–June 26), share prices fell for 1,395 out of 1,795 KOSDAQ-listed companies (77.7%). Only 46 (2.6%) were unchanged, and just 354 (19.7%) rose.
The stock with the steepest decline was BYON, down 98.84% from the start of the year. BYON halted trading after grounds emerged last year for a substantive review of listing eligibility, and its share price plunged recently as liquidation trading began. Prove it, NPX, Noble M&B, IM, and other stocks facing delisting ranked high in decline rates.
Excluding delisted stocks, about 20% of the top 100 decliners by industry were bio and healthcare corporations, the highest share. Next were IT, AI, and software at about 13%, and content, games, and media at about 11%.
The No. 1 gainer on the KOSDAQ was Taihan Fiberoptics, which surged 513% from the start of the year. Investor sentiment improved sharply after Jensen Huang, Nvidia CEO, emphasized the importance of optical communication technology at GTC 2026. Jusung Engineering (497%), GigaVis (429%), PSK (410%), and BL Pharmtech (403%) followed.
More KOSPI stocks also fell than rose, but the results were better than the KOSDAQ. Over the same period, 683 of 945 KOSPI-listed companies (72.3%) fell, while 247 (26.1%) rose and 15 (1.6%) were unchanged.
On the KOSPI, the corporation with the largest decline was Aprogen (-80.52%). Iljeong Industrial (-79.8%), Aprogen Biologics (-76.67%), GeneOne Life Science (-72.74%), and VIVIEN (-70.48%) followed. Bio and consumer goods and apparel sectors made up many of the top decliners.
The top gainer on the KOSPI was Samsung Electro-Mechanics (681%). The rise reflected its strengthened competitiveness in multilayer ceramic capacitors (MLCC) and expectations for expanding demand for artificial intelligence (AI) servers. Daewoo Engineering & Construction (376%), SK Square (367%), Samwha Capacitor (346%), SK hynix (310%), and Gaon Cable (299%) were also among the top gainers. Samsung Electronics rose 183%, ranking 15th.
Brokerages said market polarization deepened as buying by investors concentrated in large-cap semiconductor stocks. Lee Jae-won, a researcher at Yuanta Securities Korea, said, "Individual investors made large net purchases on the KOSPI since the start of the year but exited the KOSDAQ, and after the launch of single-stock leveraged ETFs, the flow toward large-cap chip stocks intensified even further."
If chip strength continues, the KOSDAQ's relative weakness is likely to persist for the time being. Lee said, "If the current chip rally centered on Samsung Electronics and SK hynix and the strong-results large-cap rally continue, KOSDAQ underperformance is inevitable," adding, "With flows concentrated in large caps and earnings momentum markedly weaker than the KOSPI, the KOSDAQ will find rotation difficult except in technically oversold phases."
Still, the KOSDAQ jumped 8% on the day as bargain hunting flowed in. As the KOSDAQ index fell below its 120-day moving average and slid to its lowest level of the year, the view spread that the decline had been excessive.
There are calls to rebalance portfolios, as selective gains based on earnings are expected on the KOSDAQ in the second half. Kim Doo-eon, a researcher at Hana Securities, said, "Given the introduction of a promotion and relegation segment, stronger efforts to remove distressed corporations, and expanded investment by the Public Growth Fund in advanced strategic industries, investors should respond by focusing on corporations that benefit from policy, show earnings improvement, and resolve AI infrastructure bottlenecks rather than expecting an indiscriminate rebound."