Optimal Monetary Policy in a Currency Union: Implications of a Country-specific Cost Channel

There is growing empirical evidence that the strength of the cost channel of monetary policy differs across countries. Using a New Keynesian model of a two-country monetary union, we show how the introduction of a cost channel (differential) alters the optimal monetary responses to union-wide and national shocks. The cost channel makes monetary policy less effective in combating inflation, but it is shown that the optimal response to the decline in effectiveness is a stronger use of the instrument. On the other hand, the larger the cost channel differential, the less aggressive will the optimal monetary policy be. For almost all parameter constellations, our welfare analysis suggests a clear-cut ranking of policy regimes: commitment outperforms the Taylor rule, the Taylor rule outperforms strict inflation targeting, and strict inflation targeting outperforms discretion.