Exactly - that's how I got the numbers above. 50% of the black population = 6% of the total population = 8.3% of the white population. My point is to assume self-interest on the part of the publication; it may or may not be representative of deeper unconscious bias in the population (there's no rule against both self-interest and unconscious bias being true), but a simpler explanation is that the Brookings Institute wanted to make their finding sound more dramatic.

Incidentally, phrasing it as "8% of whites need to consciously seek out diversity to end racial segregation" makes the problem seem eminently solvable.

It seems reasonable to give the 50% statistic, because it may show why blacks may be more reluctant or unable to participate in this mass movement. It's easy for a white person to say sure, let's move, given that there's only an 8% chance of any specific white person having to actually move.