One-factor term structure models for interest rates can be simplified and analyzed using the Vasicek or CIR processes. A new Shifted-CIR model allows for negative interest rates while maintaining simplicity. Comparing U.S. and German yield curve data, the Shifted-CIR model outperforms the Vasicek model in terms of forecasting future yield curve movements. Time-varying interest rate risk premiums in these models do not improve forecasting accuracy.