I have been hearing from both people who have recently left the LDS Church as well as some who attend meetings but are considering leaving that they perceive that the number of local ward members who are actually active seems to be declining.  Others report that missionary conversion rates are declining.  Others speak of the high percentage of missionary companions who have left the LDS Church.

Here's an interesting quote from the Mormon Social Science Association–

“. . .regarding retention rates…  the LDS Church does not release this information.  But there are ways to estimate this and several researchers have done so, giving us our current best estimates.  For instance, Rick Phillips (2006), using census data for a variety of countries, compared the membership information supplied by the LDS Church in its annual almanac to the self-reported membership identifications of people in those countries and found that the LDS Church over-estimated its membership.  The actual number of Mormons in those countries ranged from 20%  to 70% of what the LDS Church claimed.  The major implication of this finding is that retention rates of Mormon converts are fairly low.”

You can read the rest of this very interesting article here.

For more information, see The Mormon Mirage 3rd Edition:  A Former Member Looks at the Mormon Church Today(Zondervan, 2009). Also available as an audiobook and as an expanded-text E-book for Nook, Kindle and other reading devices.