As per May 2011, there is no official penis size study that have been carried out in Africa. There is also no studies that have been performed among the afro-american men population only. The common knowledge of black penises is only based on pornographic movies and rumours. charts and figures that are found over the internet are HOAXES. None of them are based on any reference.
I do admit there is an over-representation of well endowed afro-american pornstars in the US porn industry. The black population only makes up 13% of the US population. In 10 male porn stars, there is more than 1.3 black well-endowed porn star for 8.7 white well endowed porn stars However, the porn industry is not representative of the whole male population. Some people explain the large black penis in porn movie by the ghetto effect. I am not sure about it. For instance, actor Lexington Steele was a former trader who decided to leave his successful career in banking.