The causes of the substantial increase in contraceptive prevalence in developing countries since 1960 have been intensely debated. An important unresolved issue concerns the relative contributions of changes in fertility preferences (such as increases in the proportion of women who want no more children) versus improved implementation of established preferences (such as increased contraceptive use among women who do not want another child). Contraceptive prevalence data from the World Fertility Surveys and Demographic and Health Surveys for 26 countries in Latin America, Asia and Africa from the 1970s to the 1990s are analyzed through regression decomposition. The aim is to determine how much of the change in prevalence can be attributed to changes in fertility preferences (referred to as “composition”) and how much is due to changes in rates of contraceptive use within preference categories (“rates”).