In general, the women I have negotiated with will say 45k is not enough and they need more, but not give a number. I will then usually give a nominal bump to 48k or 50k. Company policy wont let me bump more than 5k over the initial offer unless they specifically request more. On the other hand, men more frequently will come back with a number along the lines of 65k to 75k, and I will be forced to negotiate down from there. After this phase, almost all women will take the offer or move on to somewhere else, not knowing they could have gotten more if they asked.