Counterfeiting as Private Money in Mechanism Design

We describe counterfeiting activity as the issuance of private money, one which is diffi cult to monitor. Our approach, which amends the basic random-matching model of money in mechanism design, allows a tractable welfare analysis of currency competition. We show that it is not efficient to eliminate counterfeiting activity completely. We do not appeal to lottery devices, and we argue that this is consistent with imperfect monitoring.