To be fair, most salary gains come through negotiation. Men tend to negotiate more aggressively than women, so it logically follows that men would tend to get higher salaries than women. I've met women in the same field as me with salaries as high or higher than mine; it's no coincidence that they were aggressive negotiators.
If person X will accept the job at $N and person Y will accept an equivalent job for $N-5000, why on earth should the employer pay person Y $N?
Sorry, but this is one situation where I believe the person feeling they're discriminated against is at fault. Want more? Ask for it. Not happy with the offer? Don't take it. I'll bet you'll also find that shy/introverted men tend to make less than extroverted men, also as a result of trying to avoid confrontations (read: negotiating).
I'm sure there's employer-caused discrimination in the hiring process in many places, but I don't think that comes through in wages. There are of course counterexamples all over the place, but I'm referring to the overall trend.