I am a firm believer that by-in-large discrimination does not take place anymore. (At least by the average person in America.) So when there are studies that say it does, I have to think twice about them, unfortunately I don't normally have the time (or desire) as to find out where the study goes wrong. Luckily this John Stossel has found out why there is a 'gender gap' in paychecks, and his answer makes sense.
Suppose two people have equal potential, but one takes on more demanding, consuming, lucrative jobs while the other places a higher priority on family. The one who makes work the focus will be more productive for an employer than the one who puts his or her home life first. The latter will get more of the pleasures of family. So he (and it tends to be "he") will make more money, even though she would be equally productive and equally rewarded if she made the same choices.