South Korea’s stock market suffered a huge shock today. The main stock market index of this Asian country is the KOSPI, and in 2026 it played a major role in the largest growth in the large international market, driven mainly by two companies: Samsung and SK Hynix. These companies are the largest manufacturers of HBM chips (High bandwidth memory or high-bandwidth memory) on the planet, memories that are hogging data centers for artificial intelligence (AI) applications.
The boom that this technology is experiencing since the end of 2022 has affected not only the business of these South Korean companies, but also the business of American Micron Technology. The KOSPI index recorded a spectacular rise in the first half of 2026 mainly thanks to the good economic results achieved by Samsung and SK hynix, but today it declined. It fell 8.8% during the session, forcing those responsible for the stock market to make a tough decision: temporarily suspend trading for 20 minutes.
Finally, the session closed with a decline of 6.02%. The KOSPI index has lost 11.7% this week, although it is still up 20% from its 2025 value thanks to the growth achieved in the first half of 2026. In this situation, it is impossible to ignore these disturbances And the interesting thing is that the epicenter of this earthquake is not in South Korea. He lives in the United States. On Wall Street. And the huge investment pullbacks that AI-related companies have seen in recent years.
Distrust is shattering the expectations placed on AI
Samsung and SK Hynix continue to do well. Really good. The crash in South Korea’s stock market was not caused by a potential drop in sales of HBM Memory; Investors react to distrust in AI. Fears that this technology will not meet expectations. However, the implications of what is happening are deeper than we can understand a priori. The Democratic victory in the last US legislative elections has caused concern among investors.
South Korea has a serious structural problem: it relies heavily on just two semiconductor manufacturers
Democrats control both houses of Congress, which could facilitate tightening regulations governing both AI and the construction of new data centers. Some large American technology companies, such as xAI or Google, They are spending a lot of money In building infrastructure for AI that can be used by itself or rented out to laboratories that need to train and run their language models.
If regulatory restrictions slow data center construction, semiconductor demand growth may slow. And this scenario will worsen the business of Samsung and SK Hynix. This is only a possibility at this point, but distrust is enough to cause fear among investors, and their fear, as we have seen on many occasions, can lead to very sudden declines in major financial markets.
Ultimately, investors’ biggest fear is that AI will never be profitable. And South Korea has a serious structural problem– highly dependent on only two semiconductor manufacturers. Samsung and SK Hynix come to represent 55.5% of the KOSPI index’s market capitalization, according to the Korea Economic Institute of America. This is a problem. To a large extent, the behavior of the entire South Korean stock market is determined by these two companies, and turmoil such as the one occurring has the potential to upset it.
Picture | Samsung
More information Reuters | Samsung | SK Hynix
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