WASHINGTON — Rich and poor Americans are slowly but surely staking out separate lives. Increasingly, they have been moving to different communities, and more frequently they are also marrying people of similar income and educational backgrounds. This is a phenomenon social scientists call assortative mating.
In 2005, 58 percent of wives with a high school diploma were married to men with the same amount of education, new research by economist Jeremy Greenwood of the University of Pennsylvania and three colleagues shows. In 1960, by contrast, only 42 percent of wives with high school diplomas were married to men with the same level of education.
The phenomenon is happening at the top of the education distribution, too. In 2005, 43 percent of wives with college degrees were married to men who also had college degrees. In 1960, the share was 33 percent.
What are the effects of this increased marital sorting? For one thing, it contributes to income inequality. If marriages occurred randomly across educational categories, Greenwood and his co-authors show, the Gini coefficient for household income in the U.S. in 2005 would decline to 0.34 from 0.43. (The coefficient falls as inequality decreases.) That would more than offset the entire increase in inequality that has occurred since the late 1960s. (This comparison is not entirely fair because even in the late 1960s, some assortative mating occurred. Nonetheless, it shows how large the effect is.)
Marital sorting also affects women's participation in the workforce. Since the 1970s, the correlation between the wages of husband and wife has doubled, Christian Bredemeier and Falko Juessen of the University of Dortmund found. Over the same period, wives of high-income men have increased their working hours more than wives of low-income husbands have.
In the 1970s, wives with high-earning husbands tended to work fewer hours than other wives did. Assortative mating changed the pattern.