The Amish population boom. Actually, the analogy isn’t exact, because to my knowledge the Amish don’t actively convert, or if they do, they aren’t that successful. At least not when compared to the Mormons, who convert and retain in-group homogenization of norms very very well. at least over comparative time. Allotropic religious speciation, anyone?
But really, the success of any major religion dwarfs all of the above.
H/T: Tyler Cowen