Riess devotes chapter 2 to a look at the missionary experience. The upshot of this chapter is “[it is a] great statistical likelihood that returned missionaries who served the full tenure of their assigned time will remain as lifelong members of the LDS church.” No surprise there (despite the fact that I personally am a statistical outlier). “Only 9 percent of those who were active growing up and served a full-time mission are no longer Mormon today, compared to 29 percent who served partial missions and nearly half, 45 percent, who didn’t serve at all.” These statistics might indicate that missionary service is actually far more important to retention than conversion, as conversion rates have slowed in recent years.
What I find most interesting are the 2013 statistics she cites about why missionaries return home early: mental health issues (36%), physical health issues (34%), a previously unresolved transgression (12%), and disobeying mission rules (11%). She recounts an interview she had with a missionary who was sent home for a physical ailment. He recites the “devastating” impact this had on his life.