Since the end of World War II, economists have tried to figure out how poor countries in the tropics could attain standards of living approaching those of countries in Europe and North America. Attempted remedies have included providing foreign aid, investing in machines, fostering education,...

The urgency of reducing poverty in the developing world has been the subject of a public campaign by such unlikely policy experts as George Clooney, Alicia Keyes, Elton John, Angelina Jolie, and Bono. And yet accompanying the call for more foreign aid is an almost universal discontent with the...