While I think JR makes some valid points, I would not be so quick to discount the effect of the "park fliers"

At my field, I see A LOT of interest in these planes, and I do not mean just the little trainers, but instead the massively powerful/maneuverable 3D profile planes.

Now I can only conclude that the popularity of these planes is nationwide. As such, I am sure that MANY that were in a "mariginal" club situation (ie crappy members, officers, dues, facilties, politics etc) have found more and more enjoyment from these park fliers, and they have gradually dropped out out of the club field scene.

If you ask me, that is where a great number of the missing members went.....don't need club or club field, then they don't get the AMA either...hand in hand.