The past several decades have witnessed a rebirth of global labor mobility. Workers have begun to move between countries at rates not seen since before World War One. During the same period, economists' study of international migration has been framed by a particular textbook model of location...

The most basic economic theory suggests that rising incomes in developing countries will deter emigration from those countries, an idea that captivates policymakers in international aid and trade diplomacy. A lengthy literature and recent data suggest something quite different: that over the...