Trend inflation and monetary policy rules: determinacy analysis in New Keynesian model with capital accumulation

The paper analyzes the effect of positive trend inflation in the framework of a standard New Keynesian model with Calvo price setting and capital accumulation. We are building on the work of Carlstrom and Fuerst (Carlstrom, Charles T., and Timothy S. Fuerst. 2005. “Investment and Interest Rate Policy: A Discrete-Time Analysis.” Journal of Economic Theory 123: 4–20.) and Ascari and Ropele (Ascari, Guido, and Tiziano Ropele. 2007. “Optimal Monetary Policy under Low Trend Inflation.” Journal of Monetary Economics 54 (8): 2568–2583., Ascari, Guido, and Tiziano Ropele. 2009. “Trend Inflation, Taylor Principle, and Indeterminacy.” Journal of Money, Credit and Banking 48 (1): 1557–1584.) who separately considered effects of capital accumulation and trend inflation in a similar context. It is shown that the simultaneous presence of positive trend inflation and capital accumulation greatly affect the determinacy property of equilibrium under this setup. Namely, in the presence of positive trend inflation the determinacy region shrinks, and it is virtually impossible to produce a determinate equilibrium with the Taylor-type rule given a steady state of inflation of more than 5%. Even for a moderate value of 2.5%, the design of the rule that ensures the uniqueness of the equilibrium requires detailed knowledge of the parameters of an economy. We also show that for a large set of plausible parameters, the standard Taylor rule leads to indeterminacy. Alternative monetary policy rules such as interest rate smoothing, output growth targeting and price level targeting are also analyzed. It is shown that the latter improves the determinacy of the model solution, and the best way to guarantee the determinate equilibrium is to use price level targeting in the policy rule.