A large portion of users are not listed in the users page. For example by roughly calculating the number of users on super user using formula
#perpage * #pages one gets 103K users. However looking at the field total_
users on http://api.superuser.com/1.0/stats shows 130K users. That's a 20% difference. on stackoverflow the numbers are 1,223K and 1,504K with a 19% difference. So the question is what is the criteria for the excluded users and why are they excluded.