I've started tracking author gender (to the extent that it's possible to guess based on names and other information) for submissions in our database.
In the first three months of 2003, we received 644 submissions. Of those, at least 60% were by men, at least 34% were by women, and 6% were by authors whose genders I'm not sure of.
So somewhere between 1/3 and 2/5 of the stories we've received so far this year were written by women. (Or, to put it another way, the number of subs by men is one-and-a-half to two times the number by women.) That's higher than the roughly 20% that I think GVG said he gets at F&SF, but it's not the 50% that I would've guessed a few months ago.
The numbers for the first three months of 2002 are roughly comparable. In that period, stories by men: 56%; stories by women: 31%; unknown author gender: 13%. (I've put more effort recently into figuring out author genders where it's not immediately obvious from their names.)
For the first three months of 2001: 53% by men, 28% by women, 18% unknown.
That 2001 unknowns percentage is high enough to make it hard to draw useful comparisons. But it's certainly plausible to guess that the percentages have been holding roughly steady. When I did a very rough informal count in June of 2002, the numbers came out almost exactly the same as the more formal first-quarter-of-2003 numbers cited above.
Oh, and overall numbers since we first started taking subs: 57% by men, 29% by women, 14% unknown.
Too sleepy to draw any conclusions. Perhaps in an editorial or article at some point, with some more number-crunching to back it up.
(I was going to post an entry explaining why I'm so sleepy, but I got sidetracked. That'll have to wait for another time too.)
In the meantime, if you want some more author-gender stats, take a look at the Broad Universe statistics page.
Okay, back to reading subs for me for a little longer, then sleep.