Note that these researchers define an “active” user as one who has posted a Tweet in the last two months. This is a very different definition than the standard “MAU” definition of “active” which means having used the site at all in the last period.

One definition isn’t better than the other but it is worth noting that opening Twitter, looking at a lot of Tweets, seeing a lot of ads, and not posting any Tweets is a behavioral pattern much more commonly seen in humans than in spambots.