September 7 was Labor Day in the United States, and the NYSE was closed. Seoul traded as usual: SK Hynix gained about 8.3%, Samsung Electronics 5.7% and KOSPI 4.6%. SK Hynix outpaced both Samsung and the index.
The latest complete US session remained September 4, when Micron rose roughly 6.1% and semiconductor ETF SMH 2.6%. Those closes were already available before Korea opened on Monday. Seoul added a day’s prices; New York had no same-day stock-market close.
Historical backfill: compiled October 4, 2026, with observations limited to the date discussed. Korean data run through the September 7 Seoul close; US references stop at the September 4 New York close. Sources: NYSE holiday calendar; Yahoo Finance historical prices for SK Hynix, Samsung, KOSPI, MU and SMH. Changes use each market’s preceding session close. The holiday is not treated as a zero-return observation. Explanations are research judgments. The securities 000660.KS, 005930.KS, MU are discussed solely as subjects of analysis, not as KSINQ recommendations to buy, sell or hold. The cited price changes reflect historical performance and do not imply future results. This article presents personal research and opinion for informational purposes only and does not constitute investment advice.