Ravallion identifies conditions under which the urban  sector's share of the poor population in a developing  country will be a strictly increasing and strictly convex  function of its share of the total population.  Cross-sectional data for 39 countries and time-series  data for India are consistent with the expected theoretical relationship.

The empirical results imply that the poor urbanize faster than the population as a whole. But the experience across developing countries suggests that a majority of the poor will still live in rural areas long after most people in the developing world live in urban areas.