That would be an interesting study. I'm agnostic, never been
   atheist - wasn't my thing. Also, never had much of a need to
   thump my chest and yell I HAVE A PENIS EVERYBODY!. I'm male, no
   question and never had an issue with gender identity but I never
   felt a need to assert gender identity much with others. So if it
   turned out that among non-believers, there were a higher
   percentage of agnostic among women than atheist among women, and
   a higher percentage of atheist among men and a smaller
   percentage of agnostic among men, that would be logical to me,
   from a subjective pov.