Women and minority groups have always been under represented in rock music, but as others have alluded to that's hardly a surprise when the majority of record label bosses are white males, and the record-buying demographic has traditionally been white kids fed a diet of boybands and photogenic but talentless gimmicky dross.
That said, I've seen Courtney Barnett, Anna Calvi, PJ Harvey, Savages and The Joy Formidable this year, so there are some women breaking through the glass ceiling, albeit not near enough.