On Compatible Multi-issue Group Decisions
Umberto Grandi, Gabriella Pigozzi

Abstract:
A crucial problem in the design of multi-issue group decisions is the
definition of rules that select outputs that are consistent with
existing correlations between multiple issues. A less known problem
arises when the collective outcome is supported by none or by the
fewest individuals, bringing into question the compatibility of a
collective decision with respect to individual choices. The aim of
this paper is to make a first step into providing a definition of
compatible outcome for binary aggregation procedures. We provide
several definitions of compatibility, both for complete binary ballots
and for the more general case of allowing abstentions in the
individual judgments. We define a number of rules that draw
inspiration from the literature on argumentation theory, social choice
theory and belief merging, and for each of these rules we investigate
their behaviour with respect to compatibility and consistency, and we
study their social choice theoretic properties.