So far I only got the number of registered users of this forum, which is ok, but not a scientific figure I could quote in my work.
Speaking as an ex academic I would have thought that it was a scientific figure and would be very quotable in your paper.
It illustrates the number of people feeling they have something to say about the Arduino, eather asking or answering. It is not as if there are other rival forums of any size to dilute or provide duplicate numbers.