In the existing literature in both sociology and economics, this phenomenon has mainly been attributed to individuals’ conscious preferences for assortative mating.
In 1960 25% of men with university degrees married women with degrees; in 2005, 48% did.
On the other hand, economists have explained assortative mating by stressing complementarities of marriage partners’ attributes.
For example, Becker (11) showed that, under a market equilibrium, marriage partners are likely to be associated in traits that are complementary in producing household goods.
Thus, assortative mating could result from selection, not by rational choice, but by the dynamics of social structures.
Assortative mating—marriage of a man and a woman with similar social characteristics—is a commonly observed phenomenon.