The disparity in the number of male and female bylines might very well have something to do with the artwork featured on their books. Cover art informs readers of a book’s contents, and publishers certainly try to manipulate readers, as Eugenia Williamson explains at the Boston Globe:
Harbach’s all-text cover has a hand-drawn, cursive script (for ladies) on a navy blue background (for men). It is done in a deliberately casual style, reminiscent of letterpress posters and jars of artisanal pickles, that’s become graphic shorthand for “young, hip, serious novelist.” (See also: selected works of Jonathan Safran Foer and Emma Straub.)
So what does it say when there’s enough cover art featuring faceless women to generate a GoodReads list with more than four hundred titles? Female writers are being treated differently even before readers open a book.