Group identification: An integrated approach

Consider social decision rules identifying two or more groups by aggregating individual opinions on who belong to which group. We search for rules respecting cross-group independence in the aggregation process. This independence axiom or its variants, together with other implicit constraints in the two models by Miller (2008) and Cho and Ju (2017), characterize a restricted family of rules; the only "democratic" rule in this family is the liberal rule. Our new framework provides a unified perspective on the main results of the two papers and uncovers implicit constraints in their modeling. Once those constraints are weakened, there emerge a richer family of independent rules including the consent rules (Samet and Schmeidler, 2003). The standard majority rule and many other democratic rules lying between the majority and liberal rules are examples. We also provide a characterization of the consent rules. (C) 2020 Elsevier Inc. All rights reserved.