# Strategy-Proof Exchange under Trichotomous Preferences

Strategy-Proof Exchange under Trichotomous Preferences

We study the exchange of indivisible objects without monetary transfers when each agent may be endowed with and consume more than one object. We assume that each agent has trichotomous preferences in the sense that she
(A) partitions objects into desirable and undesirable ones,
(B) considers a bundle unacceptable if it contains undesirable objects that she was not already endowed with, and
(C) ranks acceptable bundles by their numbers of desirable objects.
On this domain, we show that there is an individually rational, Pareto-efficient, and strategy-proof mechanism that is also computationally efficient.