A Correction in Elementary Public Choice Geometry

This paper corrects a long-standing errorin elementary geometrical constructionsthat involve collective choices inmultidimensional settings. The seeminglyinnocuous assumption of separability amongarguments in individual utility functionsdoes not imply symmetric indifferencecontours in shared goods space. Sharedgoods necessarily become gross substituteswhen resource or budgetary constraints areintroduced. The corrected constructionsuggests that issue-by-issue voting is lessefficacious than is indicated in theconventional analysis.