I came across this article on average penis size.
Doctors in the U.K. have reviewed over 60 years of scientific research concerned with the size of men’s penises, and concluded that the belief that men of different races have differently-sized penis is pure urban myth. The various studies, which measured tens of thousands of penises found that the average erect penis is between 5.5 to 6.2 inches in length 4.7 to 5.1 inches in girth, with no variation among different ethic groups. However, they did manage to create a new urban myth. According to the research, homosexual men have slightly larger penises on average than straight men.