Here are a couple stories trying to explain (or not) income disparities. First, John Ray notes a USA Today article in which black women of equivalent education are reported to outearn white and Asian women. Why?

...the tendency of minority women, especially blacks, to more often hold more than one job or work more than 40 hours a week, and the tendency of black professional women who take time off to have a child to return to the work force sooner than others.

But black men still lag behind white and Asian men even when each has the same education, which USA Today chalks up to discrimination. John points out that if you think black women make more because they work harder, then why would you not think black men make less because they don't work as hard? John also points out the poorer work histories of black men due to higher incarceration rates, but that last point doesn't hold up for the US -- black women are seven times as likely to be incarcerated as white women.

What could be the issue here? Joanne Jacobs points to a study by a University of Florida economist (NBER abstract here; here's a free copy of what appears to be an earlier draft) who studied scores and passing rates for Florida schoolchildren and found that those with more unusual names tended to be passed more easily because less is expected from them:

I suggest that teachers may use a child's name as a signal of unobserved parental contributions to that child's education, and expect less from children with names that "sound" like they were given by uneducated parents. These names, empirically, are given most frequently by Blacks, but they are also given by White and Hispanic parents as well. I utilize a detailed dataset from a large Florida school district to directly test the hypothesis that teachers and school administrators expect less on average of children with names associated with low socio-economic status, and these diminished expectations in turn lead to reduced student cognitive performance. Comparing pairs of siblings, I find that teachers tend to treat children differently depending on their names, and that these same patterns apparently translate into large differences in test scores.

That which could explain the black-white achievement gap in schools could also explain the difference in earnings behavior. Because we expect single mothers to get off welfare and jobs after the reforms in the 1990s, they may already be responding with better work performance and greater level of effort. Without holding black men to the same expectations, we can well anticipate the results of studies like that cited by USA Today.

People Respond To Incentives.