An optimal linear world income tax that maximizes a border-neutral social welfare function provides a drastic reduction in world consumption inequality, dropping the Gini coefficient from 0.69 to 0.25. In contrast an optimal decentralized (i.e., within countries) redistribution has miniscule...

In Asia inequality in income between countries is more important than inequality within countries. In Africa, Latin America, and western Europe and North America, by contrast, there are only small differences between countries; inequality within countries is more important. And when countries...