There is a filter - the mods and admins on the site. The actual number of people who [at least] joined must be round 13-14K now.
We were at 10,000 on
December 26, 2003. The average of registering was 10 per day back than, which gives approximate of 12,400 members for now. But most of the number just register, and never appear thence. So our beloved mods have to hand-clean inactive accounts
cheers