The LDS Church also lists children as members. Most Christian churches do not list children as members (at least not until much older). That alone will skew the stat and make them look like they're growing at a tremendous rate compared to everyone else.
Oh Yay! So then it must be the one true church! Oh wait, what do you say? Fewer ward units were created last year than ever? Satan has such a hold on people and even the very elect are led astray...SO then it must be the one true church! Oh Yay!