US stocks experienced a downturn on Monday, September 14, 2026, primarily driven by a selloff in semiconductor shares. This decline was triggered by major figures in the artificial intelligence industry, including the CEOs of Anthropic, OpenAI, and xAI, who voiced concerns about the rapid pace of AI development and advocated for a slowdown to mitigate potential catastrophic risks. This call to slow down AI advances directly impacted companies like Nvidia Corp. and Intel Corp., causing the Philadelphia Semiconductor Index to tumble 5.9%, its largest drop in over two months. The broader S&P 500 lost 0.48%, closing at 7,620.05 points, while the Nasdaq Composite fell 0.55% to 26,187.79, and the Dow Jones Industrial Average dropped 0.29% to 52,421.63.
Adding to market jitters, the benchmark 10-year Treasury yield briefly surpassed 5% for the first time since 2023. This rise in yields is a significant factor as it can make equities less attractive compared to bonds and increase borrowing costs across the economy. Analysts noted that the 5% threshold is psychologically impactful and could lead to market indigestion. The surge in oil prices, with Brent crude futures settling 1% higher at $105.68 per barrel due to supply worries, also contributed to inflation concerns. Traders are now pricing in a 90% chance of a 25 basis point interest rate hike by the Federal Reserve at its upcoming meeting.
Reactions to the AI slowdown calls were varied; US President Donald Trump criticized Anthropic CEO Dario Amodei, blaming a "SICK conspiracy" for concerns, while Canadian Prime Minister Mark Carney called for a global body to oversee AI. Microsoft also released rules limiting its own AI model development. The overall market sentiment was one of nervousness, with strategists suggesting AI stocks could fall an additional 10% to 15%. Bank stocks also saw declines, with Bank of America dipping after CEO Brian Moynihan projected at least a 10% drop in investment banking fees for the third quarter. Despite the recent declines, the S&P 500 is trading at 19 times expected earnings, its cheapest valuation since April 2025.
