"Wumi, color does not have much to do with popularity."

I think it does.

In many high schools in America, social groups tend to follow racial lines, though by no means absolutely. If you're a white or Asian nerd, there are plenty of other similar nerds for you to associate with. However, if you're a black or Hispanic nerd, there aren't so many.

For me, this never ended up being a problem because all of the nerds shared almost every class, so we ended up being a pretty tight group on our own. For a black nerd who wasn't as nerdy as I am, things were probably more difficult. He wouldn't be in all of the same classes, so he wouldn't grow as close to the nerds, but he'd still be relatively isolated from the "normal" black people.

It seems that blacks and Hispanics have a larger social disincentive for being a nerd than other groups, though that is probably on the lower end of factors that contribute to underrepresentation in the nerd population.

I don't think ethnicity has so little to do with it. In african american culture it seems, expression of peer disrespect is very powerful.

This is particularly true. Conformism is particularly strong in the black community. In college I had two good black friends. Both who grew up middle class and smart Both who were ostracized for having white friends. One liked heavy metal, computers and video games. One I roomed with for a year and he was harassed about it. We would receive threatening anonymous phone calls at all hours. If I answered, they would hang up. Eventually the campus police were able to trace the calls and we found out that it involved several people.