The media, Christian commentators, and many churches have paid significant attention to the decline of American religiosity in the past decade. Pew’s comprehensive report on the religiously unaffiliated aggregates past studies and offers a measured view of what’s changed, and what hasn’t, along with some context and theories to help congregations make sense of what the trend signifies. This report shows that, while the number of religiously unaffiliated continues to grow, some of the changes reflect an increasing alignment of what people do with how they describe it, with less-religious Americans reporting no affiliation at a higher rate than in the past. The report addresses generational changes, demographics, and beliefs and practices among the religiously unaffiliated. The report notably finds that the unaffiliated are not necessarily seeking a religious affiliation. Four theories are presented to address the underlying reasons for increasing numbers of unaffiliated people: political backlash, delayed marriage, broad social disengagement and secularization. Congregations interested in the social science research underlying many of the popular discussions about evangelism and those without religious affiliation will find this report to be indispensable.