S&P bank index fell 2.7% on Sept. 22 as AI, yield curve hit financials

The S&P 500 bank index fell 2.7% on September 22, 2026 amid AI concerns and focus on a flattening yield curve, Reuters reported. Schwab dropped 6.1%, Ameriprise 4.4%, according to Reuters. A flatter curve means long-term rates moving closer to short-term rates, squeezing lending margins. That pressure can feed through to savers and borrowers.