Smooth Multibidding Mechanisms

We propose a smooth multibidding mechanism for environments where a group of agents have to choose one out of several projects (possibly with the help of a social planner). Our proposal is related to the multibidding mechanism (Prez-Castrillo and Wettstein, 2002) but it is smoother in the sense that small variations in an agents bids do not lead to dramatic changes in the probability of selecting a project. This mechanism is shown to possess several interesting properties. Unlike in the study by Prez Castrillo and Wettstein (2002), the equilibrium outcome is unique. Second, it ensures an equal sharing of the surplus that it induces. Finally, it enables reaching an outcome as close to efficiency as is desired.