Monetary economists like rules. Traditionally, they worry that policymakers will sacrifice the long-term benefits of price stability for the more immediate gratification of higher growth. Realizing how hard it is to resist temptation, politicians have delegated monetary policy to a central bank that is independent, but subject to a mandate that constrains their discretion. This institutional setup helped lower inflation in the advanced economies from a median exceeding 10 percent in the late 1970s and early 1980s to about 2 percent by the late 1990s.

But, convinced that overly accommodative financial conditions in the first few years of the century spurred the credit accumulation that fed the 2007-09 financial crisis, there is a push to constrain central banks further by requiring that they publish and account for their actions with reference to a simple policy rule...