The Philadelphia Semiconductor Index (SOX) declined by 16% over eight consecutive trading sessions, marking its longest losing streak since 2008. The downturn, which lasted from October 6 to mid-October 2026, resulted in a total loss of more than $1 trillion in market capitalization across the semiconductor and AI sectors.
On the final day of the slide, all 30 stocks within the index closed lower. Arm Holdings shares dropped by approximately 7%, while Broadcom, Micron, AMD, Intel, Lam Research, and KLA each declined by about 5%. Before this period, the index had recorded a gain of over 60% for the year 2026.
The selloff was fueled by concerns regarding debt levels among AI cloud operators and unexpected inflation data, which sparked fears of prolonged high interest rates. CoreWeave, an AI cloud provider, saw its bond yields exceed 15%, signaling increased pressure from lenders. Its shares fell nearly 12% in a single session.
Short sellers reportedly secured an estimated $32 billion in gross paper gains during a seven-day window when the index dropped by more than 12%. The decline impacted broader market benchmarks, including the Nasdaq Composite and the S&P 500, as investors reevaluated risks associated with debt-financed AI infrastructure.
