Taylor rules with assets and credit

One thing we have learned from the last recession is that the financial sector is quite important, that its dysfunction can have important consequences, and this can happen even in the most financially elaborate economy. Some thus call for the health of the financial sector to become a component of every policy maker's dashboard. From a dashboard it is only a small step to include the financial sector into a policy formula such as the Taylor Rule.

Leonardo Gambacorta and Federico Signoretti take that step by deriving from a DSGE model a Taylor Rule that includes asset prices and the amount of credit. So far so good, but why not also include the exchange rate? And more indicators? This is not the purpose of the Taylor Rule. It was devised to be a simple guide to policy, from which you want to deviate when circumstances call you to do so, for example with unconventional policies that cannot be captured with a Taylor Rule, simple or not. The best example is when the Taylor Rule calls for negative nominal interest rates. Would anybody blindly follow this? Of course not, and this is why we should stop thinking in terms of a single equation, especially when one has several policy goals. You needs at least as many instruments as goals. The policy interest rate cannot do everything.