Tracy, I read the whole article, and note:
She found that while most women did not apply for higher jobs because they believed they needed more time and preparation, ironically, those who did apply actually had more success than their male counterparts.;-)
As for the 58% figure: those figures include part-time physicians, mostly female. I can guarantee that comparing like with like, female physicians are paid the same as men in the USA, Britain, Australasia. Actually they might be paid *more* in some specialties like gynaecology, for obvious reasons.
Re nurse practitioner/physician aide: IMHO in healthcare it comes down to accountability. I used to say "responsibility" but these days it is normal for people to claim to be "responsible" but not accountable. ;-) If there is a difference in the accountability of one group versus the other then there should be a pay difference.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1