Industrialized nations fret about their declining population, but the more pressing problem is that developing nations can't control their growth. Anew divide is opening between shortsighted industrialized societies and the world's poorest countries. It's all about babies. In Japan, in Russia, in Germany and elsewhere in what development gurus like to call "the global North," panic has set in about fertility declines, and couples are exhorted to have and are rewarded for producing more children. Economic growth demands it. Bigger retirement bills come due every year as populations age. A shrinking labor force spells disaster. So fascinated are we in...