Why is Samsung Electronics stock plunging today?

Samsung Electronics' stock experienced a significant 9.2% drop to ₩210,750 on Thursday, primarily due to a combination of macroeconomic factors and growing doubts about the AI investment cycle. The sudden rise in U.S. inflation, exceeding expectations, fueled concerns about potential further interest rate hikes by the Federal Reserve.

This prospect raised global financing costs and disproportionately impacted technology and semiconductor stocks, which are typically valued at high multiples. Adding to the macroeconomic woes, a report from research firm Gartner highlighted that approximately $3.5 trillion in global AI infrastructure investment could face asset impairment by 2030.

The report also suggested that the majority of neocloud operators may struggle to achieve financial self-sufficiency. This warning affected Samsung's memory chip business, which had been a key driver of its robust Q3 2026 preliminary operating profit of 107.4 trillion won. As a result, foreign investors, already net sellers of Korean equities throughout the year, accelerated their exits, exacerbating the selling pressure.

The Korean market bore the brunt of the decline, with the KOSPI opening at 5,673.01, down 5.6% from its previous close of 6,008.81. The Korea Exchange even deployed a sell-side sidecar early in the session following a more than 5% drop in KOSPI 200 futures. The AI chip value chain in Seoul, including Samsung, suffered a sharp decline, setting the stage for a seventh consecutive day of losses on the KOSPI, the longest such streak in nearly two years.