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To be honest, as editor I've never applied a quota to any aspect of BookBrowse whether it be the ratio of male to female authors, fiction to nonfiction or between genres, we just go with the books that look the most interesting at the time. And time of year is a factor, as the publishers definitely have preferences as to what time of year they publish specific types of books, the most obvious being that they tend to focus strongly on fiction during the summer - thus, at this time of year there's a good chance that BookBrowse's recommendations will skew towards fiction too.
Even though we don't quota, it turns out that our male:female split is (or has been to date) almost exactly 50:50. I realized this a few months ago when a debate broke out in the media about why traditional literary mags tend to review so many more books by men than women, and that triggered me to analyze our own stats. You can read about this in my blog post: Why Literary Mags Review Three Times More Male Writers Than Female: http://www.bookbrowse.com/blogs/editor/index.cfm/2011/2/11/Why-literary-mags-review-three-times-more-male-writers-than-female
Davina, BookBrowse editor