Thanks for the clarification - I thought it might be the usual exclusion of central and eastern european nations, despite data being collected by google.
I'm sure it's the usual ignoring of Eastern Europe.
Google publish data for everywhere. (At least, I see Bulgaria, Croatia, Czechia... )
I know, I was being sarcastic. This article should be flagged as it has no scientific meaning in the context of ... “European countries” as it ignores quite a chunk of data.
Google has information via Google Location Services. Have they stopped publishing public stats?