"Partner Choice, Investment in Children, and the Marital College Premium, by Pierre-André Chiappori, Bernard Salanié and Yoram Weiss
We construct a model of household decision-making in which agents consume a private and a public good, interpreted as children’s welfare. Children’s utility depends on their human capital, which depends on the time their parents spend with them and on the parents’ human capital. We first show that as returns to human capital increase, couples at the top of the income distribution should spend more time with their children. This in turn should reinforce assortative matching, in a sense that we precisely define. We then embed the model into a transferable utility matching framework with random preferences, a la Choo and Siow (2006), which we estimate using US marriage data for individuals born between 1943 and 1972. We find that the preference for partners of the same education has significantly increased for white individuals, particularly for the highly educated. We find no evidence of such an increase for black individuals. Moreover, in line with theoretical predictions, we find that the “marital college-plus premium” has increased for women but not for men."See also On Assortative Mating from Greg Mankiw.As mentioned above, we are getting these very high income households. When the government measures how equal or unequal the distribution of income is, it is often by household. So this process is increasing the difference in incomes between the poorest and richest households. The gini coefficient mentioned below goes from 0 to 1 and higher means less equal.
"A new working paper concludes:
"Data from the United States Census Bureau suggests there has been a rise in assortative mating....[I]f matching in 2005 between husbands and wives had been random, instead of the pattern observed in the data, then the Gini coefficient would have fallen from the observed 0.43 to 0.34, so that income inequality would be smaller""