Data: The verbal IQs of black northerners and especially black and white southerners have risen since the 1970s

The General Social Survey has been giving participants a vocabulary quiz since the 70s. Research indicates that this is a decent proxy for verbal IQ.

Supposedly, education for blacks in the South was awful prior to the civil rights movement.  If education makes any difference, perhaps IQ scores of southern blacks have gradually improved since the 1960s.  The graph below shows mean IQ per decade for southern (blue line) and northern (red line) blacks (N = 4,435):

Keep in mind that the sample is all adult blacks, so educational improvements for children would have a very gradual impact on the whole adult population, if any at all.  In the 1970s, the gap for the two groups was six IQ points (85 vs. 91). By the 2000s, the gap was down to three points (90 vs. 93).

Notice, too, how the means increased for both groups, especially for southerners, over this period. Perhaps southern schools have gotten better, and some other factor has boosted scores for blacks in both regions.  It could be some biological factor like nutrition, or perhaps something like more exposure to mainstream vocabulary words via television.  I'm pretty sure the same 10 questions have been used since the beginning, so the quiz hasn't gotten easier.

Here is the graph for whites (N = 24,363):

Like blacks, whites from the South gained significant IQ points from the 70's to the 2000s; four points to be specific (96 to 100). Northern whites, on the other hand, only gained 6/10's of a point, from 100.6 to 101.2.

It looks like northern blacks and especially southerners of both races benefited from something.

UPDATE: The South has gotten to be a more attractive region post-civil rights era. Perhaps part of the story is intelligent black and white northerners moving south, thus boosting the mean IQ.