A simple measure of fertility control.

We describe a simple measure of fertility control: the proportion of all births from the age-specific fertility schedule that occurs among women by age 35. This measure has broad applicability because it does not require information on marital fertility rates. When both the proportion of births by age 35 and the most commonly used measure of fertility control, m, are calculated for a population over time, they are correlated very highly. Because of increasing levels of nonmarital fertility in several developed countries, measures of fertility control that are based on marital fertility are less appropriate now than in the past.