For anyone curious enough to know, I did some math/counting:
Pages of Yog Fic Per Year on Ao3 (with 20 fics per page)
2012 — 1 page
2013 — 11 pages
2014 — 34 pages (3% were UMY) [introduction of Hats to Yog tag; 16% of fics had 1+ Hat(s)]
2015 — 61 pages (11.5% UMY) ((1.7% my own fic; 1% my UMY fic))
2016 — 36 pages (5% UMY) ((5% my own fic; 1.2% my UMY fic)) [55% including 1+ Hat(s)]
Taking a sample of the most recent 20 pages (approx the last 6 months), fics that tag any of the Hats as characters currently comprise 58.5% of fics posted to ao3.
The Hats are also all in the top five most tagged characters and ships in the fandom (minus Tross, still in the top ten), though this information on ao3’s system is somewhat suspect because of the change in tagging last year- not all tags are automatically sorted to be equal to what ao3 marks as “common”.