A note on restricted majority rules: invariance to rule selection and outcome distinctiveness

Recently, Karotkin (1993) has shown that in the symmetric uncertain dichotomous choice model the set of restricted majority rules (RMRs) is special in the sense that a member of this family of rules is always the worst rule among the potentially optimal weighted majority rules (WMRs). In the current paper we establish two additional special properties of RMRs. First, given a particular configuration of the group members' decisions, the collective choice is invariant to the selection of WMRs if it is invariant to the selection of RMRs. Second, given a particular decision profile, a potentially optimal WMR can result in a distinctive collective choice which is different from the choice of any other potentially optimal WMR, if and only if it is a RMR.     

Some measures of closeness to unanimity and their implications

This note demonstrates how certain collective decision methods ensure the selection of alternatives which are the closest to win unanimously. By using four different functions for measuring the distance between preference profiles, we obtain the equivalence between the closeness to unanimity procedure (CUP) and the Borda method, the plurality rule, the probabilistic Borda rule and the L-procedure respectively.     

SMALL PANELS OF EXPERTS IN DICHOTOMOUS CHOICE SITUATIONS*

This paper analyzes an expert resolution problem under an uncertain dichotomous choice situation. The experts share a common system of norms and therefore they all prefer the alternative that best suits their purpose. The selection of such an alternative is referred to as a correct choice. Our analysis of optimal decision rules for panels of independent experts is pursued for n-member decision-making bodies, n≤ 5. The suggested optimality criterion is the maximization of the probability of the panel's making the correct choice. Within our framework, this criterion is equivalent to the more common criterion of expected-utility maximization. For three-member panels of experts, the expert resolution problem is solved and illustrated by means of a medical application. For four-member panels, we list the three relevant decision rules, specify the conditions for all possible rankings of these rules, and, finally, present an extended consulting application. We conclude by listing seven relevant decision rules in the case of five-member decision-making bodies.