CONTEXT: In many developing countries, fertility has declined steadily in recent decades, while the average strength of family planning programs has increased and social conditions have improved. However, it is unclear whether the synergistic effect of family planning programs and social settings on fertility, first identified in the 1970s, still holds.

METHODS: Data from 40 developing countries in which Demographic and Health Surveys were conducted in 2003–2010 were used to examine associations among socioeconomic conditions, family planning program effort strength and fertility. Cross-tabulations and multiple regression analyses were conducted.

RESULTS: Variation among countries in scores on the Family Planning Program Effort Index, but not on the Human Development Index, has diminished since the 1970s. On average, fertility levels were lower among countries with better social settings or stronger family planning programs than among those with poorer settings or weaker programs; they were lowest in the presence of both good social settings and strong programs. In addition, fertility was positively associated with infant mortality and negatively associated with female education, but not associated with poverty. About half of the 2.3-birth difference in fertility between countries in Sub-Saharan Africa and those elsewhere can be attributed to differences in program efforts and social settings.

CONCLUSIONS: Policies focused on improving levels of female education, reducing infant mortality and improving family planning services can be expected to have mutually reinforcing effects on fertility decline.