How measurement changes exaggerate the growth of religious nones

Academic and popular interest in nonreligion has risen in parallel with the growth of nonreligious populations. In many cases, questions used to measure religion have been modified to better capture nonreligious identities. Little attention has been given to how these changes in measures affect the narrative about the “rise of the nones.” While there is no doubt that religiously unaffiliated populations have grown in many countries during the 21st century, we argue that the degree of such growth has sometimes been exaggerated. When measurement changes are introduced, they can have a substantial effect. We review methodological issues that affect estimates of the size of religiously unaffiliated populations and their change over time.