Do high earners marry each other?

Here's a paper that finds that they do:

Marry Your Like: Assortative Mating and Income Inequality

Jeremy Greenwood, Nezih Guner, Georgi Kocharkov, Cezar Santos

NBER Working Paper No. 19829
Issued in January 2014
NBER Program(s):   EFG 

Has there been an increase in positive assortative mating? Does assortative mating contribute to household income inequality? Data from the United States Census Bureau suggests there has been a rise in assortative mating. Additionally, assortative mating affects household income inequality. In particular, if 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. Thus, assortative mating is important for income inequality. The high level of married female labor-force participation in 2005 is important for this result.