When did J-16 serial production start? Was it right after J-11B? Last truly confirmed squadron of J-11B was spotted in 2014, I believe. Before that, J-11B was produced at such pace that roughly 24 planes were made per year. If production of J-16 could have gotten to such levels with just one year of hiatus (of smaller batch production) then by end of 2018 we should have something like 80+ planes produced. Of course, various people threw around numbers of 100 or so, but I am not sure what logic they used to get to such figures.
Certainly, SAC did expand their facilities during said timeframe. And J-15s were produced as well. And third batch of J-16 was seen with numbers of 30+ planes. But then again, we don't know if batch equals a year. Certainly with J-10 it doesn't seem to be the case. Anyway, with all these brigades rumored to be operating J-16 it would seem that 24 J-16 per year is plausible estimate, even if very rough. This Qiqihar rumor puts the J-16 at 4 different units, in addition to test and training ones. Of course, they may be sharing the unit crew and pilots with older flankers, so maybe just 12 or so planes in some units are J-16. So in reality, anything from 60-100 operational J-16 is also plausible.