The birth rates of nonhuman species are determined by biological drives and opacities. Humans are different. In most societies there are retie attempts to influence fertility through formal r „r, ?ai controls over sexual practices and age of marriage. Tit •nodern society the decision to have a baby is frequently as de i.! •ate and as calculated as the decision to attend graduate school buy a house, or move to a new state. Differences in fertility among nations, among groups within the same nation, and over time within groups have broad implications for education, health care, labor markets, standards of living— indeed the entire society, The ability to predict changes in fertility would be extremely valuable, but neither economics nor any other discipline has been able to do so consistently in the past. The economic perspective, however, does provide some helpful insights into this crucial
aspect of how we live.