lets see... a guy is offered a job for $X and he says no, he is then offered $X+x and takes the job. a woman is offered the same $X for an identical job in the same department and she takes $X.
If the woman is just as good as the guy, why would the employer want to pay $X+x for a worker when it could get the same work performed for $X?
employers ALWAYS give the lowest price first, and most men know that, and will try to bargain for a better position.(better pay/perks/vacation/etc)
for what ever reason(according to HR people i have known) women are less likely to bargain for their job.
and THAT... is not my problem.