Why has black-white skill convergence stopped?

"All data sources indicate that black-white skill gaps diminished over most of the 20th century, but black-white skill gaps as measured by test scores among youth and educational attainment among young adults have remained constant or increased in absolute value since the late 1980s. I examine the potential importance of discrimination against skilled black workers, changes in black family structures, changes in black household incomes, black-white differences in parenting norms, and education policy as factors that may contribute to the recent stability of black-white skill gaps. Absent changes in public policy or the economy that facilitate investment in black children, best case scenarios suggest that even approximate black-white skill parity is not possible before 2050, and equally plausible scenarios imply that the black-white skill gap will remain quite significant throughout the 21st century"--National Bureau of Economic Research web site.