The majority of the world's poor, by income poverty and multi-dimensional poverty, now live in countries officially classified by the World Bank as middle-income countries. Of course nothing happens when a country crosses a (somewhat) arbitrary threshold in per capita income but it does matter...

Comparing the emigration rates of countries at different stages of economic development, an inverse u-shape emerges. Although merely based on cross-sectional evidence, the “migration hump” is often treated as a causal relationship. Since the peak is located at rather high per capita incomes...