If there is an aggregate demand shock, its effect on utilization rates and inflation will result in an adjustment of the policy rate over time that is consistent with policymakers' objectives for output and inflation. In effect, the policy rule substitutes for the discipline of a money growth target in the face of aggregate demand shocks.
So what value would a reference value for money growth have if policy were in fact conducted in a manner consistent with the policy rule? First, the policy rule is an attempt to summarize the systematic responses of policymakers. Policymakers do not, of course, commit to follow such a rule.