The picture isn't completely clear from that, in my opinion. Look at the further breakdown on postings I provided for Italy.
You need to further break down the membership to those that have made postings. Even full members with no posts probably visit the site very little. I can tell you from experience with the book and other projects that these "lurkers" so to speak, don't often pay attention to emails, either. They don't contribute much and if they don't visit, not sure what they get out of it either, other than the magazine. No different than many clubs and most forums.
On the other hand, from my experience with "Pagoda Style" which sold out very quickly at the MB Museum Gift Shop, as well as Amazon and eBay, there are far more people that love these cars for some reason, than are members of any kind here. Most books went to non-members. So, plenty of Pagoda lovers and owners around the world that may not be members here.