Gary Becker on assortative marriage

I was reading Gary Becker’s book A Treatise on the Family for my economics of family class. The book is a fascinating application of microeconomic theory in the household setting. As I’m reading the book, many of the concepts and theorems that I learned from MA microeconomics class start to unfold and make much more sense. I jot down my thoughts as I read along, and will revise my notes afterwards.

In preparation for the next class, I read chapter 4 “assortative mating in marriage markets”. Becker starts off by assuming that male and female differ in only one measurable trait, A, with Am being men’s trait and Af being women’s. The major theorem on assortative mating is: a positive sorting of large Am with large Af (more capable men and more capable women) and small Am with small Af (less capable men and less capable women) maximizes aggregate output (using the “invisible hand” argument, each couple are unconsciously maximizing the total output) if and only if increasing both Am and Af adds more to output than the sum of the effects of separate increases in Am and Af.

Several points are worth noting here.

First of all, whether positive assotative matching occurs depends heavily on the degree of substitutability between women and men’s differential traits. If the Am and Af are substitutes, negative assortative matching will occur, i.e. “superior” men will marry “inferior” women.

Secondly, preferences of the male and the female only comes into play when it affects the cost of producing household commodities. Say, if a couple with similar preferences enjoy increasing returns to scale in household production, the average costs of producing household commodities will be lower because they are consuming similar goods. So they can enjoy a bigger amount of goods. This will make their marriage more favorable compared to being single.

Thirdly, there is a crowding out effect in the marriage market. Becker argues if there is an excess amount of men at a particular level of personal traits, they will tend to attract women with a lower level of traits (inferior women). Since women of a lower quality are married by these men, men with a matching quality with those women can only marry women who are more inferior. So on and so force. It is obvious that the most inferior men will have to remain single because their gains from marriage is no longer big enough to be justified.
Becker also argues the reason for the relative early marriage of women is that women’s biological traits and investment in human capital is more specialized than men to child production. In other words, women can take responsibility in child-bearing at a much younger age than men. Although the logic is quite simple, I feel it interesting to see such recognized facts being put down in economic jargons (“specialization”, for example).


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