When I was a computer science student 15 years ago at UofT, computer science was predominantly male (25% of female students sounds about right), and top of the class was even more predominantly male. Back then, graduate schools were focused on recruiting female students to help the field become more diverse, so it's not the lack of opportunities.

 If I fast-forward to today, about half of the female computer science students I knew left the field, largely because the opportunities in the fields they left for were better.

 From what I here, there is less computer science students now that there were 15 years ago. Where will all these female CEO's come from?