Polygyny and Fertility: Continuity or Change in Sub-Saharan Africa

This study revisits the polygyny‒fertility relationship in sub-Saharan Africa amid significant sociodemographic transformations, including declines in both fertility rates and the prevalence of polygyny. Using data from multiple rounds of the Demographic and Health Surveys across 23 African countries, we examine the contribution of polygyny to reductions in the total fertility rate (TFR), explore how the polygyny‒fertility relationship has evolved over time, and assess changes in the total number of children ever born, number of recent births, ideal fertility, and the desire for another child by polygyny status. Our findings show that the decline in polygyny has substantially contributed to reductions in TFR. While realized fertility-measured by children ever born and recent births-has declined for all married women, reductions have been greater among women in monogamous unions. Fertility preferences, including ideal fertility and the desire for another child, have decreased only among women in monogamous unions, while remaining stable for those in polygynous unions. Additionally, except for children ever born, we find minimal variation in fertility outcomes by wife's rank within polygynous unions. Taken together, these results underscore the complex influence of marriage systems on fertility and highlight the distinct fertility patterns of women in monogamous versus polygynous unions.