While I don't disagree, the graph you're referring to excludes 2013-2016. (+30%)
56 karma · joined June 10, 2012
"One shouldn’t compare Medium with services like WordPress.com because, while successfully touted as such, Medium isn’t a service. It’s a magazine. The only “service” in Medium is the service that (mostly) unpaid writers do in return for the potential exposure. Authors that have their own sub-page with a picture and a list of their articles is something online magazines have implemented back in the nineties."
It's a distinction not enough aspiring writers are paying attention to.