The short answer: Wikipedia editors are volunteers and African-Americans
rarely volunteer.
The medium answer: African-American editors often edit only articles
which relate to African-American and do that in a point of view way.
The long answer: large blocks of African-American are oppressed,
unemployed, poorly educated, and computer illiterate. Those that are
educated and prosperous tend to be too busy, and as said, are not in the
habit of volunteering.
Another matter, although lip service is paid, few African-Americans have
an interest in Africa, at least not enough to read and edit Wikipedia.
African-Americans who live in ghettos in the inner city do bear some
resemblance to Roma, the educated not so much; they are generally not
entreprenurial as Roma are; they tend to take salaried jobs.
All that said, we need to be as welcoming as possible, create good
Wikipedia editing projects for them to plug into, and reach out when the
opportunity arises.
Fred Bauder
...Wow. Maybe you can follow Phoebe's example and cite some evidence?