> Racism was more blatant and institutional in the past than
> it is today.
Yes, these days it's much harder to spot, but it's just as bad -- if not worse -- and it's no less "institutional" than it was. Since using "mere skin color" to discriminate is now illegal (and such bad form!), racists have had to use other markers that have a high degree of correlation with "blackness" in order to exclude ... such as: lack of a college education for jobs that don't actually require it ("Would you like a bookmark with that?"); whether or not you can be branded with 'criminality' (drug testing for jobs that don't require you to not be stoned; criminal record searching for jobs where you aren't likely to commit crimes on the job); and initial economic factors ("need-a-job-to-get-a-job" or putting malls out in the middle of nowhere, requiring a car to get to work [cf suburban resistance to mass transit because it will 'bring a bad sort' out to them]), etc.
> If barriers to mobility created by racism were the main culprit, one
> would expect the reverse trend - black mobility increasing as the
> racism decreases, instead of increasing.
So maybe your measure of racism "decreasing" is at fault here? If you don't get your expected change in the output, maybe the input didn't actually change?
> One can speculate what those other than racism factors may be.
That's what we count on you for! :-)
> My conjecture is the spread of Black counterculture,
> especially "gangsta culture" ...
I think you have it backwards; 'gangsta culture' is caused by and is in reaction to the continued exclusion-by-other-means. "If you won't let me into your circle, I'll make my own circle ..."
/jordan