I for one would expect women to on average have a lower pay, because they tend to get pregnant more often then males. Several months with lower pay, and missed promotions and whatnot. I have no idea how big of a difference that would make, but it makes sense to me that there is some kind of difference.
That accounts for some of it. However they had checked the pay gap between women who haven't gotten pregnant and men and saw there is still a wage gap.
Originally the idea was that MAYBE women are getting paid less because the company is paying them less BECAUSE they might get pregnant...
Yet what they discovered later on is that men and women act differently in a work setting and that men in the typical workplace environment will seek out wage increases far more then women will.
Which some people concluded that it is because "Men are more aggressive" So thus the solution muuust be that we shouldn't allow any negotiation right?
Which later we also found out that isn't true. Women will in fact seek pay increases and promotions more aggressively then men IF they are told they are able to and actually start to do better than men.
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In otherwords... everytime people make an assumption about men or women we have to go through an annoying period of assumptions until we actually hunker down and actually do work.
It is why Gender Studies is a outright toxic environment because you get people who just sort of throw their assumptions at the wall and point to a statistic as proof even though statistics are rarely proof. "Ohh this group has a 20% female participation rate! MUST be because of sexism!"... and then later on they find out it is because that job in that town is favored by highschool dropouts and that women tended to get their education more often.