Blue Tyson has a fascinating analysis of the gender breakdown in SF/F publishing. In the first analysis, Tyson breaks down the authors' gender with regards to SF/F books published in 2006. In that year, 45% of fantasies were written by woman, compared to 55% written by men. For SF books, only 21% were written by women.
In the next analysis, Tyson examines how many men and women published short stories in SF/F anthologies and collections from 1984 to the present. The findings: 84% men, 16% women. Kudos to Blue Tyson for the analysis and for giving people some good food for thought.
BTW, here are some comments I've previously made with regards to gender diversity and submissions in SF/F.