Do you really think that CIOs are defined by gender?, if your response is yes, then the next question is with other jobs/roles can be defined by gender ?
Are you more sexiest that the rest?
Why are more males truck drivers ?
Why are more females retailers ?
Why are lot more females in the fashion world than males?
Because people choose to do so (or the circumstances apply), have you seen a lot of females geeks, sure you don't. So how do you expect those few and well prepared woman to rise in a higher rate and males?.
That is not a issue, is just a percentage.