The Fourth Reith Lecture highlights population growth as one of the four main challenges to ending poverty

The fourth challenge is the continuing surge of population. Fertility rates are still so high in rural Africa that populations are doubling each generation….this excessive population growth, is susceptible of practical and proven solutions. Fertility rates in rural Africa are still around 6 children or more. This is understandable, if disastrous. Poor families are worried about the high rates of child mortality, and compensate by having large families. Poor families lack access to contraception and family planning. Girls often are deprived of even a basic education, because the family cannot afford it, and are instead forced into early marriage rather than encouraged to stay in school. And the value placed on mothers' time is very low, in part because agricultural productivity is itself so low. With few opportunities to earn remunerative income, mothers are pushed - often by their husbands or the community - to have more children.

Yet, as shown by countless countries around the world, fertility rates will fall rapidly, and on a voluntary basis, if an orderly effort is led by government with adequate resources. Investments in child survival, contraceptive availability, schooling of children, especially girls, and higher farm productivity, can result in a voluntary decline in total fertility from around six to perhaps three or lower within a single decade. But these things will not happen by themselves. They require resources, which impoverished Africa lacks.