We were careful to preselect our data pool so that physical attractiveness (as measured by our site picture-rating utility) was roughly even across all the race/gender slices. Whatever it is, white males just get more replies from almost every group.
In many cases, their response rate is one and a half times the average, and, overall, black women reply about a quarter more often that other women.
Whether it’s due to talkativeness, loneliness, or a sense of plain decency, black women are by far the most likely to respond to a first contact attempt.
Other experiments have done similar research and came in with similar results: OkCupid actually tested out response rates in correlation to race.