Over at Strange Horizons, the editors have done their yearly assessment of the state of gender in genre publishing. The good news is that men and women are published in almost equal numbers. The bad news is that books by men are reviewed far more often. So when women get published, you rarely hear about them.
The editors surveyed books reviewed in 2012 at 14 science fiction journals. They compared review numbers to numbers of books received by SF publishing industry journal of record, Locus. Their one caveat is that Locus may not have received a small number of books that are scifi and fantasy, if those books were marketed as mainstream fiction.
Here you can see that women and men are publishing in almost equal numbers. Fewer women are published in the UK than in the US.
And here are the numbers on how many books by women are actually reviewed in major journals. As you can see, the numbers do not match up, except in the case of Locus and CSZ (which actually reviews more women than men). In many cases, the discrepancy is profound, with most journals reviewing about 25% books by women, or less. This despite the fact that 45.8% of books in the genre are published by women.
What could account for this discrepancy? One possibility is that more men than women are reviewing books. As you can see, at two of the top SF journals in the field, Analog and Asimov's, there are no female reviewers at all. (Interestingly, Asimov's is run by a woman.) These numbers may offer evidence that men don't like to read or review books by women, and so there's a bottleneck when it comes to getting notice of new books by women out there. It's also possible that there's something a lot more complicated going on.
These charts show one of those complications. Though men and women are published in mostly equal numbers, at least in the US, they are not represented equally in science fiction. Roughly 25% of SF books are by women, while roughly 50% of fantasy ones are. So the discrepancy in reviews may reflect that people of both sexes prefer to review science fiction novels, and eschew fantasy. It's hard to say whether this is a function of sexism or not, but there is certainly a stereotype that fantasy is a less "serious" genre because it's female-dominated.
What is for certain, as the Strange Horizons editors note drily:
As in previous years, in the majority of the SF review venues surveyed, disproportionately few books by women were reviewed, and disproportionately few reviews by women were published.
Read the full article, including a lot more charts and analysis, at Strange Horizons.