Sub-Saharan Africa has a high incidence of polygyny. Countries in this region are also characterized by large age gaps between husbands and wives, high fertility, and the payment of a brideprice at marriage. In monogamous countries, on the other hand, the bride's parents traditionally give a dowry (negative brideprice) at marriage. Sub-Saharan Africa is also the poorest region of the world. In this paper I ask whether banning polygyny could play any role for development in Sub-saharan Africa.

Since this experiment does not exist in the data, I address the question using a formal model of polygyny and analyze the effects of enforcing monogamy within the model. I find that enforcing monogamy lowers fertility, shrinks the spousal age gap, and reverses the direction of marriage payments. The capital- output ratio and GDP per capita increase. The reason is that when polygyny is allowed, high brideprices are needed to ration women. This makes buying wives and selling daughters a good investment strategy that crowds out investment in physical assets. I show that these effects can be large quantitatively. For reasonable parameter values, I find that banning polygyny decreases fertility by 40%, increases the savings rate by 35% and increases output per capita by 140%.