Try this for some interesting stuff (you'll need Adobe Acrobat Reader or something similar, 'cause it's in pdf). Or just consider the following, from the Salt Lake Tribune of July 24, 2005:

On this day, 158 years ago, Brigham Young and his band of pioneers arrived in the Salt Lake Valley, starting a migration that quickly turned Utah into a Mormon-dominated desert realm.
   That domination - at least in terms of raw numbers - appears to be nearing its end.
   Within the next three years, the Mormon share of Utah's population is expected to hit its lowest level since The Church of Jesus Christ of Latter-day Saints started keeping membership numbers. And if current trends continue, LDS residents no longer will constitute a majority by 2030.
   These projections are based on normally secret membership counts the LDS Church voluntarily hands over to Utah's Office of Planning and Budget, under what it assumed was a binding confidentiality agreement. The state planning office uses the county-by-county numbers to help estimate future population growth.

The whole thing is here.