Why men earn more than women

Not because of discrimination:

I asked Farrell, "But apart from the 25 nonsexist reasons men earn more, isn't sexism still a factor?" He responded, "There are instances of discrimination against both women and men, but on average, no. If you knew you could hire a woman for less than an equivalent man, you'd hire women to get a price advantage over your competition. Do you think businesses so hate women that they hire more expensive men even though they'd lose so much money?"

If you want to discriminate, you have to pay the cost. Of course, this is why we do not (nor did we ever need) a single anti-discrimination law. I suggest Lew Rockwell's "The Economics of Discrimination" for those of you with any remaining doubts.
link: http://www.lewrockwell.com/rockwell/economics-discrimination.html