On the contribution of demographic change to aggregate poverty measures for the developing world2005

"Recent literature and new data help determine plausible bounds to some key demographic differences between the poor and non-poor in the developing world. The author estimates that selective mortality-whereby poorer people tend to have higher death rates-accounts for 10-30 percent of the developing world's trend rate of "$1 a day" poverty reduction in the 1990s. However, in a neighborhood of plausible estimates, differential fertility-whereby poorer people tend also to have higher birth rates-has had a more than offsetting poverty-increasing effect. The net impact of differential natural population growth represents 10-50 percent of the trend rate of poverty reduction. "--World Bank web site.