Since management traditionally consists of men, it is easy to see where the glass ceiling comes from, and that it will not disappear unless we make a conscious effort. Turning to supply, and women themselves have a role to play here, several causes present themselves.
Women are less self-confident than men, are not as quick to think that they’re suitable or to push themselves forward. That is not just my impression, it has been confirmed by psychological  BIS Review 12/2003  1  research. Another factor is that women sometimes have other preferences in respect of combining their career and family.