In the Logic of Life, by Tim Harford, the author suggests that a high incareration level of African American men has reduced the supply of eligible men in the marriage market. In Iowa, there's a disproportionate number of black men who are institutionalized relative to white and hispanic. That means that there are less black men eligible for marriage. In econ 101 language, the supply of men has shifted to the left. In order to make themselves more attractive to black men, black women go to college to increase their human capital. These same women also learn how to raise children without a male counterpart and develop jobs skills far superior to institutionalized men.
According to the Logic of Life, the black men who are not behind bars, can be very choosy about who they marry since there are 3 black women to every 1 black male. Can I add that those black men who are not behind bars must be more highly educated, more prone to work, and less affiliated with gangs so society views them as "better"? These men are accutely aware that they are in high demand so they are selective about whom they marry. Man civilian noninstitutionalized African males simply choose not to marry and play the field. What's left is a number of nonmarried black females who earn more than black males.
Every word in every chapter is significant. If you read one book this year for economics, read this one. Tim's treatment of Thomas Schelling's chessboard is brilliant and compelling. Mr. Harford shows again and again who marginal changes result in equilibrium.