I have given this subject some thought (as I am sure most of you have). One realization that I had was that as a person, I was a terrible negotiator. As a matter of fact, I would take what the HR person was offering. I remember being sooooo grateful to be hired into my first job. I just said, yes! of course! when can I start!
After some time and experience, I realized that the longer I stayed where I was, the slower my income would increase.
Fast-forward - I now have experience, I've grown up as a person (OK, not totally), I have a better understanding of how the corporate hospital model works and I know my own worth.
Now, I know that (if one works in a non-union state for a corporate or even remotely competitive hospital) HR has a chart. They've mined the data, seen what everyone else in the area in paying and picked a range of numbers. Usually, this is tied to years of experience.
Now when they give me the number, I push the wiggle room that I know they've built into their offer.
I think it's a potentially volatile generalization but I'll put it out there; women (in general) don't negotiate - men do.