It's often claimed that "80% of women want 20% of men" and such but I'm skeptical of this fact. Can somebody show me evidence that this is true? I mean when I look around, most men and women (at least of the older generation) seem to be married, which would be contrary to this claim.

It doesn't make much logical sense to me that the great majority of women would all flock to a small minority of men. Firstly, there is no way that the man can possibly commit to all of them. Secondly, isn't that basically polygamy? If you look at the data, societies with polygamy (such as those in the Middle Easy) have very poor outcomes for women, with higher rates of domestic abuse, maternal mortality, etc. Statistically, monogamy benefits women. Since women are supposedly the gatekeepers, why would they do something that would go against their interests?