So delving further into the question Cora Buhlert left a long and interesting comment that I thought I’d quote in full here:
SFF is the last bastion of the custom illustrated cover in adult fiction. Most other genres have moved to photographic covers using stock photos. And even SFF is moving that way, partly due to the rise of self-publishing, since self-publishers often cannot afford custom illustration. But even trade publishers are relying more and more on stock art (and there are a few covers here I think are based on stock art), because stock photos and stock art are cheaper than commissioning an artist. e.g. You can find a lot of decent exploding spaceship type CGI images, if you browse the stock art sites. And with stock art, the image itself usually comes before the artist (though I know at least one excellent SF stock artist who’s female).
Now the question is, why are there so few female SFF artists, especially since the art directors at the publishing houses are often women, e.g. Lauren Panepinto or Irene Gallo. This raises a few additional questions: Are there fewer women commercial artists in general? Do women illustrators tend to work in other areas, e.g. children’s books, comics, greeting cards, fashion illustration, etc…? Are women pressured to work in those areas or do they work there willingly? Is there a conscious or subconscious bias against female artists at publishing houses?
Phantom is correct that publishers prefer to work with established artists, which is e.g. why Bob Eggleton or Larry Elmore or Michael Whelan (who doesn’t appear here) have been around for decades. The question is, are those established artists more likely to be men and if so, why? One possible explanation I can think of is that cover art was often supposed to appeal to men, so maybe male artists were believed to be more likely to produce art that appeals to men. Though pulp artist Margaret Brundage and her scantily clad damsels in distress would belie that idea.
For example, the ridiculous clinch covers featuring a half-naked man engaged in a torrid embrace with a woman about to fall out of a dress of dubious historical accuracy, that were common on romance novel covers into the 1990s, were never actually supposed to appeal to the overwhelmingly female readers, but to the overwhelmingly male truck drivers working at the distribution companies, who stacked paperback spinner racks at drugstores, gorcery stores, etc…. The distributors and their truck drivers are long gone, but their taste continues to influence book covers via established artists that have been around for a long time. Similarly, the tendency for YA novels to feature a girl in a ball gown on the cover, even if no ball gown ever features in the novels, was supposedly due to the (female) YA buyer at Barnes & Noble really liking those covers. Even Baen’s famously awful covers must appeal to someone. And interestingly, I see a lot of self-published science fiction authors attempting to imitate Baen’s covers rather than the IMO much better covers of Tor or Orbit or Roc or DAW.
Besides, there are several established and popular female SFF artists, e.g. Julie Dillon, Galen Dara, Cynthia Sheppard, Kinuko Kraft, Rowena Morrill, but for some reason none of their covers appear here.
The last point, in particular, raises an issue with having an award for book covers. If this was a serious award (e.g. if there was a Hugo for Best Cover rather than Best Artist), then by not looking at a body of work, the nominees are likely to skew more male – which wouldn’t be good. The Hugo awards “Best Professional Artist” and while I’ve found that an annoying category, it is possibly a better option than “Best Cover”.
Also, by way of comparison, I looked for some different kind of data here: https://www.kirkusreviews.com/issue/best-of-2015/section/picture-books/?page=1
I looked at picture books primarily because illustrators are credited, often with equal billing as the author (or the artist is the author). As picture books are aimed at children, we might expect to find more women represented because of traditional gender roles and stereotypes (maybe).
I didn’t chase down the bios of these artists, and so just did a quick count using traditional female names. If in doubt, I counted the name as maybe not a woman.
Of the 62 names I counted, 28 had female names. The number of women artists listed is probably a bit higher. Either way, it looks like a very plausible 50/50 split.
That means we can throw away as implausible the idea that women just don’t pursue book illustration as a career or that women somehow can’t cope with the publishing industry or a whole bunch of other nonsense. I’ve also been looking for data on numbers of art-directors at publishing houses that are women but without much success. I think many may be women but that is just an impression I’ve got from a few notable names.
Perhaps more plausibly, is whether SF/F art in general has skewed male. That sounds plausible but rests on stereotypes of fandom being inherently male that are dubious. Alternatively, slow turnover of artists into the field may have resulted in the artists publishers turn to being predominately male because of conditions that existed 20-30 years ago.