Say you’re a Bangladeshi taxi driver struggling to survive on your daily wage in Dhaka. A couple of nongovernmental organizations have offered you help, but you can pick only one form of assistance: access to microcredit, or a chance to work in the United States. What’s the better deal? According to a recent analysis by the Center for Global Development, microcredit loans might net you an extra $700 over the course of a lifetime. Working stateside, you’re likely to make the same amount in a month.

Nothing rich countries can send the global poor—not loans, not textbooks, not fair-wage campaign materials—will boost the income of the average worker nearly so much as letting him walk among the wealthy. Transported from Haiti or Nigeria to the United States or Canada, a low-skilled worker will watch the value of his labor jump more than 700 percent—instantly. Wage gaps of that magnitude have some economists, notably Harvard’s Lant Pritchett, supporting a small but potentially revolutionary shift in the nature of economic cooperation: a global guest-worker program, run by rich countries in the interest of the poor. Every wealthy country would hand out enough work visas to increase its labor force by 3 percent, and the visas would be temporary, allowing the benefits to be broadly shared among successive waves of foreign workers.