[FabHK]

Two objections:

1. The 80/20 rule is a rule of thumb that happens to apply in many fields, but you can't take it as a general law and stipulate that "Probably the top 20% [0] of men are involved in the 80% of heterosexual sexual couplings". It's an empirical question.

2. "the same is true of the top 20% of women". No, probably not. The statistics for men and women look quite different (which goes to show that you can't just apply the 80/20 "rule" willy-nilly).

[scarmig]

Yes, empirical data is necessary for both, and it exists for both (I'm sure people will be posting that data, and I'm too lazy to look it up myself), but I'd bet an arbitrary amount of money that the top 20% of men get closer to 80% of the couplings than 20% of the couplings. It's an almost equally good bet that the top 20% of women get closer to 80% of the couplings than 20% of the couplings.