I formulate a political-economy model of a fiscal union where the threat of secession imposes a limit on fiscal redistribution between regions. I argue that the trade-off between implementing the region's preferred fiscal policy and benefiting from inter-regional risk sharing depends on the nature of economic shocks. Specifically both correlation of shocks across regions and their persistence over time are important. The gains from inter-regional risk sharing are potentially large when shocks are negatively correlated and temporary. In contrast, unions with negatively correlated permanent shocks are likely to prove politically unviable.
fiscal federalism risk sharing disintegration median voter optimum currency areas