It's widely known that low educational attainment, neighborhood racial segregation, and a biased criminal-justice system are detrimental to Black Americans' ability to climb the economic ladder. But Richard Reeves, a policy director at the Center on Children and Families at Brookings, has found that marriage also plays a part.

Marriage across racial lines has shot up in the past few decades, and a Pew Research Center study found that in 2010 about 15 percent of all new marriages in the United States were between couples of different ethnicities, more than double the rate in 1980.

Asian women were most likely to marry outside their own race, followed by Asian men. And an Asian man who married a White woman held the highest median income ($71,800), according to the Pew study. Black women, however, were among the least likely to marry outside their own race. That wouldn't mean much, except when we consider that Black men have one of the lowest educational attainment rates.

"I'm not sure it impedes social mobility, but it maintains a level of social inequality." —Economist William Darity Jr., Duke University

"There's almost a triple dimension of issues [Black women] have to deal with," said Kris Marsh, an associate professor of sociology and demography at the University of Maryland. "One, they have a low, and I quote this, 'out-marriage' rate. And two, if they do marry a Black man, they're more likely to marry someone less educated than themselves. And the other thing that's interesting is that [Black women] "... are much more likely to not marry at all."