How Do I Prove I'm Paid Less Than My Male Co-Workers?

A recent article in Newsweek discussed the continuing pay gap between men and women, and suggested some reasons why women still make less than their male colleagues. Another recent story discussed how female doctors are paid less than male doctors. I'm not going to argue here whether or not the pay gap is real. Instead, I want to discuss that, at least in some workplaces, women are paid less than men for the same work.