Strategy-proof allocation of multiple public goods

This paper characterizes strategy-proof social choice functions (SCFs), the outcome of which are multiple public goods. Feasible alternatives belong to subsets of a product set A(1) x ... x A(m). The SCFs are not necessarily "onto", but the weaker requirement, that every element in each category of public goods A(k) is attained at some preference profile, is imposed instead. Admissible preferences are arbitrary rankings of the goods in the various categories, while a separability restriction concerning preferences among the various categories is assumed. It is found that the range of the SCF is uniquely decomposed into a product set B-1 x ... x B-q, in general coarser than the original product set, and that the SCF must be dictatorial on each component B-l. If the range cannot be decomposed, a form of the Gibbard-Satterthwaite theorem with a restricted preference domain is obtained.