Simple: Migration. See the great article by Michael Clemens about this: http://www.huffingtonpost.com/michael-clemens/the-south-pacific-secret-to-breaking-the-poverty-cycle_b_8135780.html
From the article:
“What’s working against poverty? International labor mobility. So you might think that projects like this — among the most effective ever evaluated — would be at the center of the global antipoverty agenda. You might think that the World Bank and other aid agencies would scour the globe for similar opportunities, as a centerpiece of their activity. You’d be wrong.”
I strongly recommend reading the entire article.
The curious incident of DD on the Web 