People, People, People

Diplomats and demographers, economists and family planners, the elite brigades of global social science, will converge on Mexico City next week to tackle a formidable issue: the relentless growth of world population. They will hear some good news. In the ten years since the last United Nations-sponsored International Conference on Population, which was held in Bucharest, the annual growth rate of the world's population has declined from 2% to 1.7%.

But that positive statistic stands out amid an otherwise sobering array. During the past decade, the number...