Center for Social Information Sciences (CSIS) Seminar

Abstract: Integrating aggregation problems (Arrovian social choice, classification, group identification, etc.) and allocation problems (social choice with transferable utilities, claims adjudication, cost or surplus sharing etc.) in a unified model, we establish an equivalence of independence of irrelevant alternatives (Arrow 1951), non-manipulability by reallocation (reallocation-proofness), and decentralizability. We provide a full characterization of collective decision rules satisfying any of the three equivalent axioms: they are represented as the sum of two components, the first is a default decision and the second is the weighted average of additive decisions in some key variables of the model. The representation theorem is used to derive several central results in the two strands of literature and to establish new findings, in particular, in group identification and classification problems.

Written with Biung-Ghi Ju.