Two weeks ago, I took a snapshot of entry counts for each tag on the fandoms page at Archive of Our Own, hoping to eventually get a sense of which fandoms were growing fastest. Comparing that data with the entry counts on the site today, I think it might be possible to understand which fandoms are growing most quickly.

Unfortunately, a simple count of how many times each fandom’s tag was used is going to be imperfect—maybe much more misleading than my BoardGameGeek reports. Evidently, AO3 tag counts can fluctuate quite a bit: their names can change; tags can reportedly be reclassified such that their new parent tags suddenly get credit for existing entries; and the archive accepts mass uploads of fanfic from old repositories / personal collections such that work written long ago can suddenly show up as if it were new.

Still, it’s something. I’ll start with the top 25 fandoms by a raw count of new entries appearing in the past two weeks:

∆       %∆      Total   Fandom
----    -----   ------  ------
3218	0.023	143559	K-pop
3105	0.013	241238	Marvel
2792	0.013	220048	Marvel Cinematic Universe
1619	0.038	44004	Voltron: Legendary Defender
1572	0.026	62339	방탄소년단 | Bangtan Boys | BTS
1278	0.063	21405	僕のヒーローアカデミア | Boku no Hero Academia | My Hero Academia
1263	0.008	167506	Real Person Fiction
1249	1.892	1909	Detroit: Become Human (Video Game)
1215	0.01	118844	The Avengers - Ambiguous Fandom
1214	0.011	115916	The Avengers (Marvel) - All Media Types
1185	1185.0	1186	Metalocalypse (Cartoon)
1116	0.007	169996	Harry Potter - J. K. Rowling
1034	0.009	116772	DCU
1011	0.01	98215	The Avengers (Marvel Movies)
936	0.005	184710	Supernatural
715	0.01	72436	Star Wars - All Media Types
706	0.017	42992	Original Work
607	0.009	65714	Captain America - All Media Types
568	0.098	6376	Firefly
557	0.01	58797	Captain America (Movies)
498	0.005	93744	Teen Wolf (TV)
462	0.034	13870	Spider-Man - All Media Types
451	0.004	113953	Sherlock Holmes & Related Fandoms
423	0.072	6285	NCT (Band)
397	0.013	30213	Final Fantasy

Honestly, the most surprising items are things like Firefly, the tag count for which has likely been skewed by one of the factors I mentioned above. Only Detroit: Become Human pops out as the kind of fast-growing category I’m sure I’m looking for (though I have doubts about the game itself). So a raw count of new entries is probably not very helpful for discovering newly popular / fast-growing fandoms.

So here’s a list of every fandom that had more than 25 new entries in the past two weeks, that grew by more than 4.0%, and that had more existing entries two weeks ago than it has gained in the past two weeks (a criterion that will eliminate things that are really too new to judge; for example, assuming it has real growth potential, I’ll have to catch Detroit: Become Human next time, because it’s more important to weed out name changes and weed out percent changes that only seem large because the population is too small):

Total   ∆       %∆      Fandom
-----   ----    -----   ------
21405	1278	0.063	僕のヒーローアカデミア | Boku no Hero Academia | My Hero Academia
6820	298	0.046	Dungeons & Dragons - All Media Types
6376	568	0.098	Firefly
6285	423	0.072	NCT (Band)
4936	365	0.08	Spider-Man: Homecoming (2017)
4637	256	0.058	Critical Role (Web Series)
3999	181	0.047	New Dangan Ronpa V3: Everyone's New Semester of Killing
3245	255	0.085	Sanders Sides (Web Series)
3211	174	0.057	全职高手 - 蝴蝶蓝 | Quánzhí Gāoshǒu - Húdié Lán
2068	104	0.053	Black Panther (2018)
2061	105	0.054	Figure Skating RPF
1508	91	0.064	Doctor Strange (2016)
1449	65	0.047	Buzzfeed Unsolved (Web Series)
1329	94	0.076	Bendy and the Ink Machine
1307	51	0.041	RuPaul's Drag Race RPF
1116	90	0.088	Far Cry (Video Games)
1104	83	0.081	Timeless (TV 2016)
1093	75	0.074	Stray Kids (Band)
1006	148	0.172	偶像练习生 | Idol Producer (TV)
955	66	0.074	Deadpool (Movieverse)
889	49	0.058	Fire Emblem Heroes
833	45	0.057	MacGyver (TV 2016)
772	46	0.063	Fate/Grand Order
753	30	0.041	Falsettos - Lapine/Finn
724	49	0.073	Simon vs. the Homo Sapiens Agenda - Becky Albertalli
676	52	0.083	The Arcana (Visual Novel)
671	48	0.077	Disney Duck Universe
663	43	0.069	13 Reasons Why (TV)
633	38	0.064	Doki Doki Literature Club! (Visual Novel)
633	38	0.064	Call Me By Your Name - All Media Types
583	36	0.066	The Worst Witch - All Media Types
570	85	0.175	Far Cry 5
539	45	0.091	Love Simon (2018)
531	52	0.109	Trollhunters (Cartoon)
517	28	0.057	龍が如く | Ryuu ga Gotoku | Yakuza (Video Games)
511	31	0.065	Call Me By Your Name (2017)
497	114	0.298	NINE PERCENT (Band)
481	36	0.081	The Worst Witch (TV 2017)
441	99	0.289	Ocean's (Movies)
409	30	0.079	Ginga Eiyuu Densetsu | Legend of the Galactic Heroes
399	62	0.184	Splatoon
374	27	0.078	Humans (TV)
369	38	0.115	DuckTales (Cartoon 2017)
361	43	0.135	BanG Dream! Girl's Band Party! (Video Game)
304	34	0.126	Granblue Fantasy (Video Game)
295	56	0.234	凹凸世界 | AOTU Shijie | AOTU World
293	28	0.106	Eurovision Song Contest RPF
265	27	0.113	Boruto: Naruto Next Generations
245	41	0.201	The Incredibles (2004)
193	45	0.304	Flight Rising
179	34	0.234	Garrison's Gorillas
121	30	0.33	HiGH&LOW: the Story of S.W.O.R.D. (TV)

I’m not positive this is the best way to look at the data, but there sure are plenty of things here I’ve never heard of and would like to know more about.