Financial factors and monetary policy: Determinacy and learnability of equilibrium

This paper contributes to the debate whether central banks should respond to asset prices, credit spreads and other financial factors in setting monetary policy, by evaluating determinacy and expectational stability of equilibria under various monetary policy rules. With adaptive learning, beliefs constitute an additional set of state variables, which may require more than a response to inflation, that has traditionally been argued in the literature as sufficient to achieve central bank objectives under rational expectations. Furthermore, financial frictions are introduced by extending the determinacy and adaptive learning methodology embodied in Bullard and Mitra (2002) and Bullard and Mitra (2007), beyond the New Keynesian modelling framework by incorporating a Financial Accelerator (Bernanke, Gertler and Gilchrist 1999). A key result is that monetary policy rules responding to lagged asset prices and credit volume have less desirable determinacy and learnability characteristics than responding to current asset prices and credit spreads. This conclusion dovetails with recent research such as Gilchrist and Zakrajsek (2011) and Gilchrist and Zakrajsek (2012), who show that signals derived from credit spreads contain information which help explain business cycle fluctuations and demonstrate that a credit spread augmented monetary policy rule dampens cycle variability. Another result is that the conclusions in both Bullard and Mitra (2002) and Bullard and Mitra (2007) are robust to a New Keynesian model with financial frictions.