There's a project here, for somebody whose command of statistics is better than mine, namely disentangling the black-white gap from the general increase in inequality. Perhaps it's already been done?
We know that the rich are getting richer and the poor poorer, since, what, the mid-70s? Now at that time blacks on average were considerably poorer than whites, due to a history of racism in theory and practice, stretching back decades, centuries even. Has the further impoverishment and immiseration of blacks proceeded more rapidly or gone beyond the comparable stats for a sample of whites who started out with the same distribution of incomes and wealth as blacks had, when the ongoing Great Revanche began?
Put another way: the perpetuation and even the aggravation of a gap that existed when the Revanche began is a predictable result of the Revanche itself, other things being equal. Has the aggravation been greater than the normal statistical effects would predict?