Fixed interest rates over finite horizons

We consider finite horizon conditioning paths for nominal interest rates in New Keynesian monetary policy models. This is done two ways. First, we develop a simple way to use policy interventions in the form of interest rate shocks to achieve the conditioning path and show this yields a unique solution. We then modify this method to generate an infinity of solutions making the model better behaved but effectively indeterminate. Second, we use two-part rules where a specially designed targeting rule generates fixed interest rates endogenously over the initial period before reverting to a more conventional instrument rule. We show that the two approaches are equivalent. We discuss appropriate selection criteria over the resulting equilibria.