Re numbers: this is a direct link to the Disqus profile of John P. Capitalist, the hedgefond manager who does financial estimations and often posts at The Underground Bunker (Tony Ortega's blog). Scroll down to load a lot of posts, then use the browser to search for terms like "numbers", "members", "membership", or "basics" (book sales).
A recent defector, I forgot who, had good information about the numbers of "basics" packages sold, which where pushed for a long time on ALL Scientologists. That number, too, was ridiculously low; particularly if taking into consideration that members were urged to buy more than one box (which many did). The members who didn't buy any either must have been in very bad financial shape or can be considered as "under the radar" type members, with little or no belief left and no sympathy for CoS, yet trying to keep a low profile for example so as not to have their family torn apart by disconnection from family members who too are Scientologists and are still take orders from CoS.
Another good indicator for membership numbers and also the percentage of "under the radar" members is the attendance at events. For big events, like the opening of the "Super Power" building, was and is put enormous pressure on ALL Scientologists worldwide, staff and public, to attend, but even then they didn't scrape up more than 10000 or so.