The Effect of Strategic Behavior on Group Decisions

According to HARSANYI, the social utility of an alternative in a group decision voting game is the sum of all voter utilities for that alternative. With random member utilities, the expected social utility is defined as the mean of the random variable social utility. The social utility for a decision rule depends on the number of alternatives, group members, the distribution of member utilities, and strategic considerations of the group members.In this paper, the effect of strategic voting behavior on the expected social utility is computed and compared for three well known voting procedures: The Single Vote-Rule, the Borda-Rule and the Hare-Rule. It is assumed that each member has complete information about the others' utilities as common knowledge, and that individual strategic considerations lead to a HARSANYI-SELTEN-equilibrium as the outcome strategy combination of the voting game. According to the HARSANYI-SELTEN-Theory, the resulting equilibrium depends also on the members' prior distributions about other members' voting behavior. The effect of different of such priors is also discussed.