One of the church's primary responsibilities is to foster genuine spiritual growth in people's lives. Today's pastors bring tremendous effort and passion to this task, but they are often disappointed by people who sit in the pews for years, knowing about Jesus but never really knowing him. In 2004, Willow Creek Community Church in suburban Chicago undertook a three-year study to measure spiritual growth called the REVEAL Spiritual Life Survey. Over the next six years, additional data was collected from over a quarter million people in well over a thousand churches of every size,...