Employing a political-economics approach, this paper compares small states and unions when the former fail to internalize cross-border externalities of publicly provided goods. It discusses two types of unions: federations with more than one level of government and unitary states. While unitary states are unable to differentiate public spending ac-cording to differing preferences, rents of governments in a federation are higher due to a common-pool problem. The comparison leads to the following results. (1) Citizens prefer small states to large states if spillover effects are weak. (2) They benefit from a multi-level government only if their preferences heavily differ from the median-voter's preferences and if spillovers are strong. Based on this comparison the paper also dis-cusses the creation of unions. Making specific assumption on the distribution of prefer-ences, it analyzes strong Nash equilibria and coalition-proof equilibria at the union formation stage.
voting theory electoral accountability federations strong Nash equilibria coalition-proof equilibria.