Higher levels of testosterone I guess.

There are inherent differences between men and women, not only in biology but also in the brain/psychology.

In general, Men have a higher diversity in IQ and Risk Taking.

The TL;DR is that Men will have a tendency to take higher risks than women, which is then rewarded more, if it succeeds, however, it is punished more severely when one fails. Punishment generally involved poverty and unemployment.

This doesn't mean women cannot take risks, just that they have a lesser inclination to.

Negotiation for a wage on your job is a form of risk taking, in case of failure you can certainly sour your work relationships which ruins your long-term income projection.

Right, I'm not disputing that there are obvious biological differences. Why do you think that the statistical difference between men and women at intellectual performance (for which I haven't seen numbers, but I'm not disputing) is due entirely to biological differences? It seems foolish to reject environmental influences off-hand.

I'm not fully rejecting environmental influences, however the biological influences play a much grander role for most of the population than environmental influences.

There will be exceptions but they're not the norm.