SKHX Down 8% as SK Hynix's Record Seoul Crash Meets ADR Arbitrage Selling

The Arbitrage Behind the Crash

SK Hynix priced the largest U.S. share sale ever by a foreign company — a $26.5 billion Nasdaq ADR offering — and the receipts popped roughly 13% on their Friday debut. Then Seoul opened Monday and the *common stock* did the opposite. That split is the whole story.

The ADRs were structured at 10 receipts per Seoul common share, and desks including UBS had already flagged the obvious trade: go long the more liquid, Nasdaq-100-candidate ADR and short the Seoul-listed shares against it. With ADR-to-common convertibility running largely one-way, that arbitrage has no clean closing mechanism, so the selling pressure lands squarely on the Korea line. On Monday it landed hard — foreign and institutional desks offloaded the common while retail rotated into the U.S. ticker. Strong New York demand and weak Seoul supply are two sides of the same position.

What Actually Tripped It

The arbitrage set the stage; a brokerage note lit it. Before the Seoul open, Korea Investment & Securities cut its Q2 operating-profit estimate to roughly $40 billion, about 8% below consensus, arguing that SK Hynix's locked-in HBM supply contracts cap its earnings upside even as conventional DRAM prices climb — the opposite of the pricing leverage the market had been paying up for.

That was enough to turn a profit-taking session into a rout. SK Hynix closed down about 15%, its worst single day on record, steeper than anything it printed in 2008. Because Samsung and SK Hynix together carry more than 40% of the index, the KOSPI tripped a circuit breaker as the benchmark fell over 8%, and the memory selloff bled into Taiwan. Crucially, the ADRs themselves gave back ground on their second session — so this was not a pure venue rotation from Korea into New York. The whole complex repriced lower on the earnings read.

Why the Perp Reads Different

SKHX does not track the Nasdaq ADR, each of which represents just one-tenth of a Seoul common share. Its oracle marks one full Seoul-listed common share and converts the KRW close to USD, so the perp wears the entire Korea drawdown — near $1,207 after roughly an 8% slide over 24 hours — while the ADR line sits behind its liquidity premium. That mechanic is why the same event looks like a modest ADR wobble in New York and a record-setting drop in the perp.

It also means two moving parts sit under the mark: the equity and USD/KRW. Monday's damage was overwhelmingly the record equity selloff, not currency, but on a quieter tape FX drift can nudge SKHX with no Seoul headline behind it. The open question is convergence: as long as the ADR holds a premium to the common and conversion stays one-way, the gap between the two lines is a structural feature, not a mispricing that snaps shut — and the perp stays pinned to the weaker of the two.