Our brother Roy Yanke at the blog Confirm identifies it in an article entitled “Finding Hope in the Midst of Conflict:

Drawing from numerous studies conducted over the last 4 decades, the experts agree that conflict – “the ugly pastor/pew rift over how the life and work of a particular church is to be understood and acted upon” (Chuck Wickman, “Pastors at Risk, p 39) – is the top reason.

Read the whole article; it’s well worth your time and there’s a great sermon illustration to boot!