Some people don't like him but Jordan Petersen does a great talk on Gender equality in work and why is can never work along with why some careers favours one gender over the other. He talks about why the Legal proffession is dominated by Females and why a quota system will NEVER work. As stated above, if you take a profession such as nursing which has a low percentage of male participants and enforce a 50/50 quota you will end up with lesser quality candidates. If you really want to 'even' things out you need to address the reasons we have a lower number of females interested in a flying career and that is a very long term project.