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...

The “Palma” is the ratio of national income shares of the top 10 percent of households to the bottom 40 percent, reflecting Gabriel Palma's observation of the stability of the “middle” 50 percent share of income across countries so that distribution is largely a question of the tails. In...