[Tangurena2]

There have been some studies that show once female participation in a field/career gets past about 40%, males tend to leave (or at a minimum, fail to enter) that field/career. Historically, school teachers and secretaries were male fields. Then in WW1, there weren't enough men available, so women were encouraged to enter those jobs. After WW1, those same jobs weren't seen as "manly" enough and male participation never recovered.