We tried to look into that also: https://www.blockdata.tech/blog/general/how-many-blockchain-...
The point of this research was to highlight that the tech is maturing and it is not some 'hobby' technology. Next to the whole 'crypto world' there is still a lot of innovation happening in Blockchain land.
As per another comment, not saying it is good or bad as is the conversation around permissioned blockchains tends to go but our role is just to share the numbers :)