Women Don't Ask by Linda Babcock is well worth reading if you're interested in this sort of thing. One particularly striking result was that MBA graduates diffe

Women Don't Ask by Linda Babcock is well worth reading if you're interested in this sort of thing. One particularly striking result was that MBA graduates differences in pay between men and women was around $4,000 in favour of men - which, IIRC, she claimed could be accounted for by the fact that 57% of men chose to negotiate as compared to 7% of women. Those who negotiated, regardless of gender, tended to receive around $4,000 more than those who did not. I think it very plausible that a lot of this sort of thing comes down to wanting to be fair, not wanting to be pushy - that sort of thing. Which generally works well with other women, but not necessarily so well if your boss is a man and prefers to communicate in a different style. Especially when your access to that style is limited by there being few gender-relevant role models; a man's aggressive he's a go-getter, a woman's aggressive she's an irrational bitch.