US chip and AI stocks tumble as Nasdaq posts worst single-day drop, erasing post-midterm gains

US chip and AI supply chain stocks suffered a broad sell-off on Thursday, with the Nasdaq Composite tumbling 5.5% in its steepest single-day decline since April 2025, wiping out all gains made since the midterm elections within just six minutes of the opening bell. The Philadelphia Semiconductor Index plummeted over 12%; Nvidia dropped about 9%, losing nearly $450 billion in market value, while AMD and Micron both plunged more than 17%. Around $2.5 trillion in market value was wiped out from the Nasdaq in a single day, fueled primarily by mounting investor concerns over real returns on massive AI infrastructure investments and a potential slowdown in data center buildouts.