SK Hynix hits 25% of Korea's stock index on AI chip demand surge

SK Hynix, founded in 1983 as Hyundai Electronics, has emerged as a linchpin of AI infrastructure despite being a mature company in a historically cyclical industry. The company manufactures dynamic random-access memory (DRAM) and NAND flash memory, which have long powered consumer electronics but have become indispensable to artificial intelligence systems. DRAM serves as temporary but extremely fast storage that allows GPUs from companies like Nvidia to ingest massive amounts of data per second during large language model training. NAND provides cheaper permanent storage for operating systems and datasets that GPUs can access continuously, though at lower speeds than DRAM.

The AI supply chain's explosive growth has lifted SK Hynix to extraordinary valuations. In the first quarter of 2026, the company held the second-largest market share globally in both NAND (18%) and DRAM (29%), and reported record earnings—revenue tripled year over year while operating profit rose more than 400%. The company's market dominance now extends to South Korea's entire stock market: SK Hynix accounts for over 25% of the Korea Composite Stock Price Index, making it by far the nation's most heavily weighted stock.

Historically, memory companies faced unpredictable boom-and-bust cycles. Demand surges would trigger years of supply ramp-up, often overshooting equilibrium and causing prices to collapse once supply caught up. However, Wall Street analysts now believe demand for DRAM and NAND will remain constrained for the next few years, allowing memory prices to climb through 2027 and potentially into 2028. This supply-constrained environment has driven extraordinary shareholder returns: according to Google, SK Hynix stock is up over 1,418% in the last five years, meaning a $5,000 investment would now be worth $75,900.

Earlier this month, SK Hynix raised $26.5 billion（約4.2兆円） by listing 178 million American depositary receipts (ADRs) on the Nasdaq exchange under the ticker SKHY, with ten ADRs equaling one South Korean share. This listing opened the company to U.S. investors, who previously had difficulty accessing the stock. At one point, SK Hynix topped $1 trillion（約160兆円） in market cap. Industry observers note that if the AI supercycle proves durable, memory companies could enjoy longer contracts and reduced cyclicality. However, analysts caution that while this memory cycle may look different from past cycles, it carries the same risk of eventual oversupply and price collapse if AI demand weakens or the trade faces major setbacks.

SK Hynix's dominant position in South Korea's stock market reflects the central role memory chips play in the AI infrastructure boom. The company manufactures DRAM and NAND flash memory, which are essential components in feeding data to the GPUs that power large language model training. Historically, memory companies were viewed as cyclical—surges in demand lead to oversupply and price crashes—but Wall Street analysts now expect demand for DRAM and NAND to remain constrained through 2027 or beyond, which would support sustained price growth and profitability.

The company's recent Nasdaq listing and $26.5 billion（約4.2兆円） fundraising mark a turning point for international investor access. In the first quarter of 2026, SK Hynix held 18% global NAND market share and 29% DRAM market share while delivering record earnings. Its five-year return of over 1,418% far exceeds major stock indices, making it a standout performer. However, the stock's concentration in Korea's index—now over 25%—and its dependence on sustained AI demand create concentration risk for Korean portfolios and cyclical vulnerability if the AI trade weakens.