The Optimality of the Friedman Rule When Some Distorting Taxes Are Exogenous

The Friedman rule is a feature of second-best policies in several monetary models. We extend this result by establishing that zero nominal interest rates can be optimal even if the Ramsey planner is not able to select many distorting tax rates. However, we show that the optimality of that policy prescription does depend on the set of tax rates the planner is able to choose. We also provide an intuitive way of assessing whether the Friedman rule is optimal for each particular set of tax rates the Ramsey planner is allowed to select.