Monotone Implementation

We study a class of direct revelation mechanisms which implement outcome functions satisfying a monotonicity condition. Monotone implementation is in dominant strategy equilibrium when values are private and in ex post Nash equilibrium when values are interdependent. The original Vickrey-Clarke-Groves mechanism is not a monotone implementation mechanism although its many extensions to interdependent value models are. The extraction mechanisms of Cremer and McLean (1985) are a special form of monotone implementation mechanisms for finite type spaces.