First, as I have emphasized in several previous speeches, communication plays a crucial role in the success of monetary policy (Mishkin, 2007b and 2007c). And in this regard, it seems virtually self-evident that communicating about a single numerical value for the inflation objective is more straightforward than communicating about an interval or range of numbers.
Of course, regardless of whether the central bank has a point objective or a comfort zone, it is inevitable that the inflation rate will fluctuate in response to various shocks; that's why it is also crucial for policymakers to communicate clearly about the outlook for the macroeconomy and about the central bank's strategy for promoting the stability of prices and economic activity.