[jaawn]

Even if this is true, this doesn't magically make it not a gender issue. What if women are generally given less leverage by default in negotiations? What if implicit gender biases have a chilling effect on women's expectations when they go to negotiate? What if women are discouraged from negotiating at all?

I think, given what I've seen so far, women are given less leverage to start with, they are subject to the chilling effects of gender biases, and they are discouraged from negotiating more often than not.

Sure, a woman can overcome these obstacles, but she shouldn't have these extra obstacles in the first place. The "pay gap" is almost certainly not due to managers thinking "oo I'll pay her less because she's a woman," but it is still indicative of some (more complex) gender inequality.

[lagadu]

If the effect is so widespread, surely it'd be financially irresponsible for any company in their right mind to hire men because women would negotiate less in the middle and long terms.

[jaawn]

I think most managers would see that as an unreliable prediction to make, and not very valuable when making hiring decisions. When hiring someone, you are solving an immediate problem, and not often thinking of the future raises the person is going to negotiate or not negotiate.

What you are saying might be true if most hiring was done by CEOs and not department managers.