Impossibilities for Strategy-Proof Committee Selection Mechanisms with Vetoes
29 Pages Posted: 10 Aug 2016 Last revised: 21 Oct 2017
Date Written: March 14, 2017
When a group of voters selects a committee out of a set of candidates, it is common and often desirable to endow these voters with some veto power. I present impossibility results showing that even limited veto power makes many mechanisms of interest manipulable. This applies in particular (i) to mechanisms the range of which contains a degenerate lottery in which a committee is chosen for sure and (ii) to mechanisms that are constructed from extensive game forms with a finite number of strategies. These impossibilities hold on a large set of domains including the domain of additive preferences, and even when probabilistic mechanisms are allowed and voters can report cardinal preferences.
Keywords: Mechanism Design, Strategy-Proofness, Veto, Probabilistic Mechanism, Committee Selection
JEL Classification: C72, D71, D82
Suggested Citation: Suggested Citation