In a conversation with a pair of great friends from Southeast Asia, they referred to a very recent study on attrition. We asked them for more information and they took us through the development. The first article to which they pointed us looked at the conversation-starter:

http://www.alifeoverseas.com/is-conflict-with-teammates-really-the-top-reason-for-missionaries-leaving-the-field/

Then they shared the post that launched the actual study itself:

http://www.alifeoverseas.com/why-do-missionaries-leave-the-field-help-us-find-out/

And finally, they shared the quantitative results of the study:

http://www.alifeoverseas.com/closer-to-the-truth-about-current-missionary-attrition-an-initial-analysis-of-results/

Needless to say, we thought they were grand. : )