Of course, it should go without saying that the world is more complicated than theoretical arguments suggest. Notably, imperfect data and the difficulties of distinguishing permanent from temporary changes will make changes in secular productivity growth exceptionally difficult to identify in real time, both for the private sector and for the Federal Reserve.
The need to discern the underlying economic forces and to react appropriately in an environment of incomplete information makes monetary policy an exceptionally challenging endeavor. 6  BIS Review 4/2005