There was an interesting thread a few months ago about the gender pay gap. Specifically that as legislation provides for equality there wasn't one. ( in the UK).
A pp provided links to some useful data on the value of gender in certain roles. Coding, for instance was originally a woman's job as it was felt that attention to detail and dexterity was a female trait and it was poorly paid. As men started to join, it changed to be thought of as a more intellectual job, a trait traditionally thought of as male and the salaries went up accordingly.
Likewise the rural fishing industry (I forget where but I'll try and find the links). Men had historically sewn the nets as it was considered complicated and the net had to be strong. These traits were valued and paid accordingly. Women did the fishing and were paid less as it was more straightforward. Gradually over time it changed and the net makers were female dominated. The fishing was considered harder and the pay switched in favour of the men doing it.
Likewise typing. Originally considered a male job as it was thought it required stamina (!). Gradually women started to do it and the pay slid down.
This one is anecdotal - when I was younger teaching was considered a more of a male job. It was also considered one of the 'professions' like being a lawyer or a doctor. Over 50 odd years, it has become female dominated and, despite being very hard, I don't believe is considered as highly as the other professions any longer.
I will try and find the link before anyone asks.