Strategy-proofness and the reluctance to make large lies: the case of weak orders

This article incorporates agents’ reluctance to make a large lie into an analysis. A social choice rule is D(k)-proof if the rule is nonmanipulable by false preferences within k distance from the sincere one, where k is a positive integer. If D(k)-proofness is not logically equivalent to strategy-proofness, then agents’ reluctance to make a large lie embodied in D(k)-proofness is effective to construct a nonmanipulable rule. This article considers weak orders as agents’ preferences. I prove that on the universal domain, D(k)-proofness is equivalent to strategy-proofness if and only if k ≥ m ? 1, where m is the number of alternatives. Moreover, I find a sufficient condition on a domain for the equivalence of D(1)-proofness and strategy-proofness.