We ask what level of migration would maximize world welfare. We find that skill-neutral policies are never optimal. An egalitarian welfare function induces a policy that entails moving mainly unskilled immigrants into the rich countries, whereas a welfare function skewed highly towards the rich...

We reexamine several bodies of data on the growth of output, labor, and capital, within the context of a model that admits the possibility of an externality to the capital input. The model is an augmented version of Paul Romer's (1987) reformulation of the Solow model. Unlike Romer, however, we...