The rise of Samsung and SK Hynix, fueled by the AI industry, has made the South Korean stock market a leading indicator for US tech sector performance. Analysts warn that the increasing correlation between the two markets is diminishing the benefits of portfolio diversification, and any slowdown in AI capital spending would amplify risks for both simultaneously.
Data shows the KOSPI (^.KS11) fell 732.09 points, or 10.84%, while the Nasdaq 100 (^.NDX) dropped 89.131 points, or 0.32%. On May 12, 2026, in the trading room of Hana Bank in Seoul, South Korea, bank staff worked in front of multiple monitors. Buoyed by a favorable market environment, the South Korean stock market opened at a record high that day.
The deep integration of capital expenditure in the AI supply chain, linking US tech giants with South Korean memory chip makers, has steadily increased the correlation between Wall Street tech stocks and the South Korean market. Data from Rayliant shows the 60-day correlation coefficient between the KOSPI and the Nasdaq 100 recently rose to 0.50, the highest since 2021. This strengthening is primarily due to the rising weight of Samsung Electronics and SK Hynix, which together account for over half of the KOSPI's total market capitalization. Both companies are at the core of the AI hardware supply chain, supplying memory chips for data centers operated by US tech giants.
Rolf Bulk, an analyst at Futurum Group, explained via email, "The rising US-Korea correlation essentially means the KOSPI is increasingly resembling a semiconductor-only index." The earnings of Samsung and SK Hynix are highly dependent on the capital expenditure of cloud giants, which also determines the profitability of US semiconductor and tech firms. Bulk noted that data center demand accounted for approximately 40% of global DRAM demand last year, a figure set to exceed 50% this year and continue climbing; DRAM is essential memory hardware for AI servers.
For Asian investors, the South Korean market can reflect the health of the global AI industry before the US market opens. Jung In-yun, founder of Fibonacci Asset Management, stated, "When there are shifts in global AI demand overnight, the South Korean market, home to Samsung and SK Hynix, provides the first liquidity trading feedback. SK Hynix, in particular, has become a core barometer because of its deep ties to HBM, one of the most critical components in the AI supply chain." Recent trading has clearly demonstrated this pattern. On July 13, SK Hynix plummeted 15% in its worst single-day drop ever, dragging the KOSPI down over 8%. The Nasdaq 100 followed with a 1.88% decline, and a host of US tech and chip stocks weakened: Micron Technology fell 4%, SanDisk dropped 12%, and Intel slipped 6%.
Peter Kim, head of global investment strategy at KB Financial Group in South Korea, analyzed that the current memory chip rally started later than the Nasdaq's, as US capital initially focused more on large cloud providers. However, this rally has been volatile, and global funds now generally view the South Korean market as a leading indicator for the entire AI sector. Samsung's earnings guidance is also one of the earliest hard indicators of AI demand each quarter, typically released two weeks before major US semiconductor companies.
Analysts emphasize, however, that US and South Korean tech stocks move in the same direction, without one consistently leading the other. Philippe Wohl, research director at Rayliant Global Advisors, said, "The ups and downs of US and South Korean tech stocks are increasingly driven by the same underlying logic: market sentiment toward the AI hardware supply chain." When major AI news breaks during US market holidays, the stock prices of Samsung and SK Hynix can pre-empt the capital flow direction when the US market opens. Conversely, if news occurs during US trading hours, the Nasdaq's performance will guide the next day's session in South Korea.
Investment Risks: Diversification Benefits Erode
Industry veterans widely agree that this rising correlation presents a clear risk. Previously, investors allocated funds to both US and South Korean stocks with the intention of hedging risk through geographical diversification, but this cross-market benefit is now significantly diminished. Bulk pointed out, "The South Korean market can no longer hedge against US tech sector risk. With half of the index's weight tied to the semiconductor cycle, any reduction in capital expenditure by cloud providers would put more pressure on the South Korean market than on most other countries." He added that South Korean memory chip stocks are inherently more volatile than many US chip companies, and flows from leveraged ETFs would amplify the price swings. Wohl shares this view, noting that AI has become the absolute dominant variable for both the US and South Korean tech sectors, erasing the primary reason investors diversify across these two markets: the advantage of spreading risk across different countries is disappearing.
Potential for Divergence in the Long Term
Peter Kim believes that the two markets could diverge again over the long term. While Micron, Samsung, and SK Hynix are all currently benefiting from DRAM price increases, differences in their capital expenditure plans, product mixes, and US domestic chip support policies will eventually lead to diverging performance trajectories. He also highlighted the rise of China's memory industry as a new variable. Although domestic Chinese manufacturers still trail global leaders in technology, their pace of iteration often exceeds market expectations. CXMT made its debut on the Shanghai Stock Exchange's STAR Market on Monday, surging 466% on its first day of trading to become the most valuable chip company by market capitalization on the A-share market.
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