It may come as no surprise that the influence of Christianity in the United States is waning. Rates of church attendance, religious affiliation, belief in God, prayer and Bible-reading have all been dropping for decades. By consequence, the role of religion in public life has been slowly diminishing, and the church no longer functions with the cultural authority it held in times past. These are unique days for the church in America as it learns what it means to flourish in a new “Post-Christian” era. Barna has developed a metric to measure the changing religious landscape of American culture. We...