I put it to you that black men are disproportionately represented in that 20%, especially when they are a minority in a society. I only have anecdotal evidence of this, I'll admit, but I have pretty good reasons for believing it's true. There is no hard data available, so it's the best i can do. African blacks are way more of a minority in Australia than the UK, so it is very clear here.
Anecdotes:
- A girl I knew ditched her hot Kenyan boyfriend. The final straw was a stranger girl cold contacting him in a mall to give him her telephone number, when she was there with him.
- Any night in bars where there is an African black. In Australia, just watch the girls compete for his favour! I was out with a girl once looking to hook up, and I asked her "What about the black guy over there?". She just said, "Nah, I don't stand a chance", looking around at the younger hotties queuing for him.
- Another time, out with a girl at a salsa class, almost the same story as above, except the girl did manage to exchange phone numbers with two African guys there, to her elation. With the competition there, she figured that as a win.
- Standing in a queue at a cafe (diner, I guess) with a 6'6 athletic African-American in front of me. A mid-30's secretary type walked past me to cold contact him, ask him where he was from, give her his number, offer to show him around "any time he wanted"
- In 2005 a black French guy lived with me for a year whilst on a placement from a university in France. He arrived as a pretty shy, romantically hopeful guy - left as a confident, multi-partner, wife and girlfriend fucking stud. My pleasure was that I constantly had hot, naked, or almost naked, women lolling around my home!
- My ex-wife tried black for the first time in Tokyo in 2009, and had about 100 consecutive black guys after that.
Do anecdotes amount to a case? Probably not. Maybe, in some of those cases, the guys were just hot - and things happen to hot guys of all race. It's just that I have never seen that sort of happen (in some of those cases) with white guys.