Ok, so why are they less likely to negotiate, why are they more likely to ascend at less valuable companies, etc. The whole point of talking about the wage gap is figuring out why it exists. And inevitably, there are only two possible ends to this investigation. Either there are inherent biological differences that cause women to be less effective and valuable in our economy, or some societal manifestation of sexism is causing these differences. As far as I can tell there is no other possible answer.