Informational Accuracy and the Optimal Monetary Regime

King (1997) develops a framework for assessing four monetary regimes: an optimal state-contingent rule; a non-contingent rule; pure discretion; and a Rogoffian conservative central banker. Using this framework we show (a) that King is wrong to claim that it implies that an optimally-conservative central banker always dominates a fixed-rule monetary regime; (b) that if the private sector has a signal of the shock to which monetary policy responds - the accuracy of which is exogenously fixed - then either the optimal state-contingent rule or the optimally-conservative central bank can dominate; and (c) that if the private sector optimally chooses the accuracy of its signal then any regime can dominate.