http://www.worldbank.org/research/growth/pdfiles/growthgoodforpoor.pdf

Income of the poor rises one-for-one with overall growth. This general relationship between income of the bottom fifth of the population and per capita GDP holds in a sample of 80 countries covering four decades. Although there is a fair amount of variation around this general relationship, a number of popular views about the poverty-growth relationship are not true. The effect of growth on income of the pooris no different in poor countries than in rich ones. Incomes of the poor do not fall more than proportionately during economic crises.In contrast we find no evidence that formal democratic institutions or public spending on health and education have systematic effects on incomes of the poor. These findings leave plenty of room for further work, because they emphasize the fact that we know very little about what systematically causes changes in the distribution of income. (Au)