The Mystery of Monogamy

This Paper examines why developed countries are monogamous while rich men throughout history have tended to practice polygyny (multiple wives). Wealth inequality naturally produces multiple wives for rich men in a standard model of the marriage market where polygyny is not ruled out. Our model demonstrates, however, that while higher male inequality generates more polygyny, higher female inequality produces a more monogamous equilibrium. Moreover, we derive how female inequality in the marriage market is higher in equilibrium as women are valued more for their quality versus quantity of children when human capital becomes more important in determining the distribution of income. As a result, male inequality in traditional societies generates inequality in the number of wives per man, but male inequality in developed societies, where human capital is a larger source of income and inequality, manifests itself as inequality in the quality of their wives. Using data from Cote d?Ivoire, we provide supporting evidence for the main implications of the model.