Some little evolution of total sold volumes:
Beginning of 2016
Haikyuu: 16k
My Hero Academia: 3,7k
Shokugeki: 8k
Black Clover: -
Beginning of 2017
Haikyuu: 22,4k
My Hero Academia: 7,5k
Shokugeki: 12,3k
Black Clover: 2,1k
Beginning of 2018
Haikyuu: 28k
My Hero Academia: 13k
Shokugeki: 14k
Black Clover: 4,8k
Just now
Haikyuu: 30k
My Hero Academia: 17k
Shokugeki: 15k
Black Clover: 6,5k
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Haikyuu has been growing 6k for year
Hero Academia grown 4k between 2016 and 2017, now 5k between 2017 and 2018, looks is going to grown 6k from here to 2019
Shokugeki has just stagnated, from growing 4k to growing only 2k.
Black Clover is growing between 2,5 and 3k.
If trend continues, 2019 should begin with Haikyuu being in 32k and Hero Academia in 19k (or even 20k), then Shokugeki in 16k and Black Clover in 7,5-8k.
Heck, in long term is very possible for Haikyuu to hit 40k and Hero Academia 30k in 2020, while Shokugeki barely reaching 20k and Black Clover 10k
EDIT: For some reason, Video Girl Ai was like 5k in 2016 and 2017 and suddenly 15k in 2018