Measuring the extent to which assortative matching differs between two economies is challenging when the marginal distributions of the characteristic along which sorting takes place (e.g. education) also changes for either or both sexes. Drawing from the statistics literature we define simple conditions that any index has to satisfy to provide a measure of change in sorting that is not distorted by changes in the marginal distributions of the characteristic. While our characterisation of indices of assortativeness is not complete, and hence cannot exclude the possibility of multiple indices providing contradictory results, in an empirical application to US data we find that all indices satisfying our conditions indicate that homogamy by education has increased over time.
The extent to which like-with like marry is particularly important for inequality as well as for the outcomes of children that result from the union. In this paper we discuss approaches to the measurement of changes in assortative mating. We derive two key conditions that a well-defined measure should satisfy. We argue that changes in assortativeness should be interpreted through a structural model of the marriage market; in particular, a crucial issue is how they relate to variations in the economic surplus generated by marriage. We propose a very general criterion of increase in assortativeness, and show that almost all indices used in the literature are implied by our criterion with one notable exception, that moreover violates one of our conditions. Finally, we use our approach to evaluate the evolution of assortative matching in the US over the last decades, and conclude that assortative matching has increased, particularly at the top of the education distribution.
The extent to which like-with like marry is important for inequality as well as for the outcomes of children that result from the union. In this paper we present evidence on changes in assortative mating and its implications for household inequality in the UK. Our approach contrasts with others in the literature in that it is consistent with an underlying model of the marriage market. We argue that a key advantage of this approach is that it creates a direct connection between changes in assortativeness in marriage and changes in the value of marriage for the various possible matches by education group. Our empirical results do not show a clear direction in the change in assortativeness in the UK, between the birth cohorts of 1945-54 and 1965-74. We find that changes in assortativeness pushed income inequality up slightly, but that the strong changes in education attainment across the two cohorts contributed to scale down inequality.