I looked at which fandoms on AO3 have the most femslash, both in terms of absolute numbers, and in terms of percentage of overall works. I also took an initial look at the amount of genderswap labeled in the F/F tag for the popular fandoms. [note: I did not yet understand AO3's system of canonical fandom tags when I did this, so the fandoms listed here are sometimes a bit odd.]
Caveat: due to processing errors, a number of fandoms did not get properly analyzed - mostly ones whose names contain non-ascii characters, but apparently also Les Mis (and possibly others). I’m not sure yet if/how that affects these graphs. But please point out to me any fandoms with a bunch of femslash that are missing!
I crawled all the fandoms on AO3 and grabbed the total number of works, and the number labeled F/F. For the purposes of this analysis, I then discarded all fandoms with fewer than 50 works (a somewhat arbitrary threshold that I chose so that I would be pointing out fandoms to people that actually had more than a handful of works — and to ensure that I didn’t analyze the rare fandoms where 100% of the fanfic is F/F because there’s only one fic :) ).
I sorted by percent F/F (Figure 1) and by overall number of F/F works (Figure 2). For Figure 2, I also did a search for fandom name + F/F + “Genderswap” to see how many F/F fics were explicitly also labeled genderswap. I did not remove strongly overlapping fandom tags for this analysis, as they were not identical in F/F makeup.
Results and Discussion
The chart and spreadsheet below give a good list of fandoms that have a high percentage of F/F works — the chart shows fandoms where the majority of the works are labeled F/F; I’m glad that there are some of those out there on AO3, even if I wish there were more! And I’m heartened to see that some of these fandoms have hundreds of F/F fanworks.
The next chart shows the 30 fandoms with the highest absolute count of F/F works, and these are almost all the same as the biggest fandoms overall. The major exceptions were Once Upon a Time, Warehouse 13, Pitch Perfect, and Rizzoli & Isles — most of which also were on Figure 1 and have a very high proportion of F/F fic.
When I did earlier analyses that discussed femslash, commenters had asked how much of that was actually genderswapped male characters. This analysis does not fully address that question, but I did look at the number of F/F fics in the (largely male-character-dominated) fandoms in Figure 2 that were labeled “Genderswap”. Those fics are shown in red.
It’s important to note that just because fic has both these tags does not mean that the F/F pairing in the fic is genderswapped — could be a different character. I also have not yet looked into how many F/F pairings involve a genderswapped character but do not use that tag. However, it looks like the amount of F/F that is genderswapped might not actually be too high in the male-centric popular fandoms — if people are doing a good job labeling their genderswap.
This is only representative of AO3. I suspect FFNet has a higher proportion of F/F (it’s less M/M-focused, in my limited analyses so far) -- but unfortunately, FFNet doesn't break things down by relationship category or ship, the way AO3 does, so it's difficult to do this kind of analysis there. I also expect that there are probably a number of F/F focused fandoms that have their primary homes on fandom-specific archives, or LJ, or other places. If anyone wants to share recs for fandoms or sites that have a high ratio of F/F, please add those in the comments!