Like Iskierkaa said, about more recent numbers.
And if you want to go a bit further back, you have this doc from the launch of SL up until september of last year. After, Blizz changed the API so we could no longer get the numbers from there(wowranks.io).
OP: Data as it currently stands
Doc: https://docs.google.com/spreadsheets/d/1cAmV40TMtljuBcgcRSHi3sH4wfjtPprFML7NGJDkl_c/edit#gid=0
You have sites such as wowgraphs showing even further back to Legion, etc. And ofc logs as well for anyone who wants to dig through those records.