Just sharing your compensation with your co workers goes a long way toward solving this problem. But it is a social more to not share this information.

There's a very rational economic reason why some people are paid less than others for the same job. Leverage. Since WWII, women entered the work force in large numbers _because they were willing to work for less than their male counterparts._ So what was an opportunity for women once has become discrimination. Rightfully so. But it's important to remember how we actually got here. Equality of opportunity often translates into inequalities of outcome for reasons that are neither good nor efficient. So, yeah, sometimes the law can tip the scales to fix this. And that is not a bad thing.