Strategy - proof Partitioning ∗ Debasis Mishra

We consider the problem of choosing a partition of a set of objects by a set of agents. The private information of each agent is a strict ordering over the set of partitions of the objects. A social choice function chooses a partition given the reported preferences of the agents. We impose a natural restriction on the allowable set of strict orderings over the set of partitions, which we call an intermediate domain. Our main result is a complete characterization of strategy-proof and tops-only social choice functions in the intermediate domain. We also show that a social choice function is strategy-proof and unanimous if and only if it is a meet social choice function. We are grateful to Shurojit Chatterji, Arunava Sen, Yves Sprumont, John Weymark, seminar participants at University of Caen, Indian Statistical Institute, and Singapore Management University for useful discussions and comments. Indian Statistical Institute University of Caen