Strategic Manipulation in Committees Using the Plurality Rule: Alternative Concepts and Frequency Calculations

This paper suggests an evaluation of the plurality rule according to how much it can be manipulated by individuals. We analyze strategic voting with reference not only to the usual notion of Nash equilibrium but also to some weaknesses of this notion, depending on the assumptions about how the individual agents choose their strategies. We provide two types of results for each concept of equilibrium: First, we give necessary and sufficient conditions for a profile to be an equilibrium when the plurality rule is used; and second, we present formulas giving the exact frequencies of unstable situations in the three-alternative case.