U.S. and Korean tech stocks are now tightly linked — and that could be a worry for investors

Bank employees work in front of multiple monitors at the Hana Bank dealing room in Seoul, South Korea, on May 12, 2026.

Wall Street tech moves and South Korea's stock market are becoming increasingly intertwined as artificial intelligence spending binds together the fortunes of U.S. technology giants and Korean memory chipmakers.

The 60-day correlation between the Kospi and Nasdaq 100 recently climbed to about 0.50, its highest level since 2021, according to data provided by Rayliant.

The growing relationship reflects the increasing dominance of Samsung Electronics and SK Hynix, which together account for more than half of the Kospi index. Both companies sit at the center of the AI hardware supply chain, providing the memory chips needed for data centres operated by U.S. technology giants.

"The correlation has increased because the KOSPI has become a semiconductor index," Rolf Bulk, analyst at Futurum Group, told CNBC via email.

Samsung and SK Hynix increasingly depend on the same hyperscaler spending that drives earnings at U.S. semiconductor and technology companies. Data-center demand rose from around 40% of global DRAM demand last year to more than half this year, according to Bulk, who expects that share to increase further. DRAM, or dynamic random-access memory, is used in AI servers.

That gives investors in Asia an early read on the strength of the global AI trade before Wall Street opens.

"Samsung and SK Hynix provide the first liquid market reaction to overnight developments affecting global AI demand," said Jung In Yun, founder of Fibonacci Asset Management. "SK Hynix in particular has become an important barometer because of its exposure to high-bandwidth memory, which is one of the most critical components in the AI supply chain."

Recent trading illustrates that dynamic. On July 13, the Kospi fell more than 8%, dragged by SK Hynix's 15% plunge and record fall. The Nasdaq 100 followed suit to end 1.88% lower that day. Shares of big technology names declined that day. Micron Technology closed 4% lower, Sandisk shed 12%, Intel pulled back 6%.