U.S. AI Stocks Tumble; Nasdaq 100 Loses $1 Trillion in Market Cap on June 23

U.S. stock markets experienced sharp declines on June 23, with the semiconductor and AI sectors leading losses. The Philadelphia Semiconductor Index fell 7.3%, while the Nasdaq 100 lost approximately $1 trillion in market capitalization if the day's decline holds. The S&P 500 dropped 1.44%, and the Nasdaq Composite fell 2.21%.

Key individual stocks declined sharply: Nvidia fell about 4% with market cap briefly dipping below $5 trillion, Intel, Marvell, and AMD lost 6-10%, while memory chip stocks Micron and SanDisk each dropped over 13%. The selloff was triggered by news that Alphabet lost two senior AI scientists, compounded by growing market concerns over the long-term costs of AI infrastructure investments.