Genes, legitimacy and hypergamy: another look at the economics of marriage

In order to credibly sell legitimate children to their spouse, women must forego more attractive mating opportunities. This paper derives the implications of this observation for the pattern of matching in marriage markets, the dynamics of human capital accumulation, and the evolution of the gene pool. A key consequence of the trade-off faced by women is that marriage markets will naturally tend to be hypergamous - that is, a marriage is more likely to be beneficial to both parties relative to remaining single, the greater the man's human capital, and the lower the woman's human capital. As a consequence, it is shown that the equilibrium can only be of two types. In the Victorian type, all agents marry somebody of the same rank in the distribution of income. In the Sex and the City (SATC) type, women marry men who are better ranked than themselves. There is a mass of unmarried men at the bottom of the distribution of human capital, and a mass of single women at the top of that distribution. It is shown that the economy switches from a Victorian to an SATC equilibrium as inequality goes up. The model sheds light on how marriage affects the returns to human capital for men and women. Absent marriage, these returns are larger for women than for men but the opposite may occur if marriage prevails. Finally, it is shown that the institution of marriage may or may not favour human capital accumulation depending on how genes affect one's productivity at accumulating human capital.