KOSPI falls 5.46% on AI-investment worries and CXMT chip news, while Brent rises 1.84% on Middle East risk

Line up the day's moves and the sizes do not match. Brent's 1.84% gain ^[5] took it from roughly $104.72 ^[10] to $106.65. The won lost 10 won, or about 0.75% ^[9]. KOSPI fell 5.46% at the point Yonhap measured it ^[14], close to three times the oil move ^[8]. Equities can overshoot a commodity shock, but a threefold overshoot in one session invites a second cause.

Yonhap supplies one. It reported that fresh concerns about AI investment led the fall ^[14], and that Samsung Electronics and SK hynix were hit hardest by news reports that China's CXMT had made a breakthrough in advanced chip technology ahead of both ^[16]. Sedaily's account runs the other way: it says Middle East risk and higher crude prices fueled risk-off sentiment ^[15]. Yonhap's report does not mention Brent or the Houthi attack, and Sedaily's does not mention CXMT or AI.

In our view the chip report carries more of the fall, because Yonhap names the stocks that were hit and the oil move is small next to the index move. The counter-case is that a Saudi attack lowers the market's tolerance for a chip scare on the same day. In that case both reports are right, and these two accounts cannot say how to split the blame.

The currency leg is easier to read. The dollar index fell 0.168 to 102.414 ^[6], about 0.16% ^[11], so the won's 0.75% slide happened against a softer dollar. Sedaily puts the pressure on foreign share sales and dollar-futures purchases ^[3] and says exporters' dollar selling limited further gains ^[6]. The won had already touched the low 1,330s the session before, its weakest in two years, according to Sedaily ^[7]. Tuesday's 10 won extended a move already under way.

We would be wrong if KOSPI keeps falling on a day when Samsung and SK hynix steady and Brent holds above $106.65, because that would put the weight back on oil. A seventh session of foreign selling with Brent lower would point the other way.