About the complex factors, that is true, for example:
* A blessed baby already counts in the records of the church until gets baptized or reach 18 years old.
* An inactive member even when join another church, stills remains in the church’s records.
* The church couldn’t be able to find out when an inactive member (not linked anymore to the church) passes away.
* The age for baptism in the church is 8 years old, in many of the other ones is older.
* LDS families are well known for a high rate of natality.
So, it is true that the growing of the church can’t be truly measured, but still is interesting that even when the church make an statement about caring less about this kind of statistics for the “news media”, still it bothers sending to them this private statistics… free publicity is always welcome.