The CCC wrote:While there are many Mormon type sects. All the others are very small relative to The Church of Jesus Christ of Latter-day Saints, and most could fit into a large living room in most American homes. The next biggest one is the Community of Christ and it has abandoned all pretense of being LDS.
The RLDS (Community of Christ) has basically become a mainline liberal protestant sect, although I'm not sure I'd say that means they've abandoned the pretense of being LDS. That didn't exactly help their numbers though. From what I can tell though they tend to see most LDS scripture as with most of the Bible as fiction with inspired lessons behind it. They are still reasonably sized despite a lot of people leaving during the controversies in the 80's and early 90's. I think the current numbers are still around a quarter of a million. There's then maybe 10,000 - 30,000 who are loosely RLDS but don't accept the main body's move to liberal protestantism.
The next two big ones are fundamentalist polygamist sects. The FLDS down near Arizona (and more recently Texas) have obviously had their legal troubles but never were that large. The numbers aren't clear although likely under 10,000 and possibly just a few thousand. The next largest is the Allred group although they've been shrinking. (There's apparently been a big move by many to try and return to the main LDS body - especially in the Montana parts) Again the numbers aren't clear but it's most likely less than 10,000. There's then a few that have around 1,000 members and maybe all the rest of the polygamist groups total 10,000 or less.
There's then maybe 20,000 - 30,000 associated with pre-Nauvoo groups such as the Temple Lot group and the Bickertonites.
Still if you add them all up there's probably at least 300,000 to possibly as many as 350,000 non-LDS Mormons.