Wall Street delivered sharply different results across major indexes in September. The Nasdaq Composite gained 1.8%, reached a record on September 22 and ended the month at 26,861.06, helped by artificial intelligence (AI) and semiconductor stocks including Intel, Advanced Micro Devices and Meta Platforms. The S&P 500 fell 0.4% and finished 1.9% below its August all-time high, while the Dow Jones Industrial Average dropped about 4.3% and the Russell 2000 declined 5.4%. Higher Treasury yields added to market pressure, with two-year and 10-year yields rising about 50 basis points (one-hundredth of a percentage point) and the 30-year yield increasing nearly 40 basis points. UBS Chief Economist Arend Kapteyn said AI investment and wealth created by rising AI equities account for at least 80% of U.S. economic growth, prompting UBS to raise its forecast for next year’s AI-related capital spending by $200 billion to $1.4 trillion. The concentration has also affected initial public offerings, with Oura, Holtec Nuclear and Bamboo Insurance postponing planned listings and Anthropic allegedly delaying its expected offering from October to November. Investors are watching the Federal Reserve’s next interest-rate decision and rising U.S.-Iran tensions, while expectations of another rate increase have eased after New York Fed President John Williams said there was no urgency for further adjustments.