South Korea's benchmark KOSPI index has surged sharply year-on-year, driven by demand for AI memory chips and an influx of retail investors. SK Hynix and Samsung Electronics alone account for roughly half of the index's market capitalization, fueling debate over how long the rally can last.
June 26, 2026 · KOSPI Watch
South Korea's AI-Memory Rally Sends KOSPI to Record Highs — and Stokes Bubble Fears
An HBM-chip boom and a flood of retail investors lifted the index up ~168% year-on-year to a record 9,385 points. But SK Hynix and Samsung alone make up about half its value — concentrating both the gains and the risk.
+168%
KOSPI year-on-year gain (as of Jun 26, 2026)
9,385
Record high in points; passed 7,000 for the first time in May
~61%
SK Hynix's share of the global HBM market (2025)
The Two-Stock Engine
HBM market share, 2025 — SK Hynix vs Samsung Electronics
~61%
SK Hynix
Nvidia HBM3E / HBM4
~17%
Samsung
Shares nearly tripled
Together the two firms make up ~50% of the KOSPI's total market capitalization . SK Hynix briefly topped a $1 trillion valuation and overtook Samsung in market value.
The Retail Investor Surge
Shareholders more than doubled in six years, minting a generation of novice investors.
+54%
retail net purchases YoY in 2025 — margin debt at record highs
The Bull Case
A pure play on the Nvidia-centered AI infrastructure supply chain
Goldman Sachs lifts 2026 year-end target to 7,000, sees 130% earnings growth
Micron's strong results and SK Hynix's US listing plans drive rebounds
The Warning
Heavy concentration in two chipmakers — cooling AI demand could swing the whole index
Circuit breakers triggered repeatedly; daily moves over ±5%
More volatile and concentrated than Taiwan's TSMC-led market (up 50%+)
The key question ahead: the surge is widely framed as accompanied by speculative mania. How long the AI-led rally can continue — and whether the two-stock concentration becomes its undoing — remains unresolved.
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