Pretty complicated topic that is discussed here: http://bionerdess.tumblr.com/post/41270871980/science-genderquote
Unfortinately I was not allowed to make comments longer than 140 signs. So I respond here.
From the psychological point of view there is a big problem in cognition that does not simplify the issue. The image of the sexes is biased. A traditional man fits the image of a leader. Strong, self-confident, …
The problem is a woman having those qualities. She migth be a good person for a leadership position. Unfortunately her character traits are not fitting the traditional image of a woman anymore. Leadership for women – as far as I can comment on that – is a balancing act. Unfortunately.
As long as those biases exist. I do not see any solution.