I'm reading Dataclysm, a book exploring online data especially related to 23andme.com (huge dating site). There is a chapter on interrace ratings which show the usual patterns, namely that euros(male and female) rate africans lower. They however mention that this isn't the case in the UK. If the theory is that mean g levels cause stereotypes which cause these rating patterns, then perhaps the africans in the UK really are smarter. Unfortunately, they don't share much of the data.
This is unlikely because the fairly representative adult (16 to 65 with mean ages of about 40) samples which I found show a difference of about 0.7 SD. These were from 2000, 2007, and 2012 (see attached, for example), plus two others from 2003 and 2011 which provided numeracy/literacy pass rates. So if there was a substantial narrowing, it was basically with the 2000 birth cohort. And I don't imagine that these kids would have been the referential point in the rating study mentioned.
(There was also an ETS SAT evaluation study in 2008 which showed a 0.7 SD or so difference. In 2012, when the MCS kids were 12 the evaluation study kids would have been in their 20s. So, again, the narrowing would have to have been recent.)