Changing survey measures and measuring change: A call for religion measurement experiments

If we want to measure change, we shouldn’t change our measures. Yet measurement changes do happen. Some result from global circumstances such as mode switches necessitated by the COVID-19 pandemic. Others are related to changes in the presentation and prevalence of a topic. The number of people who identify with no religion, also known as religious “nones,” has grown rapidly in many countries (Hackett et al. 2015; Stolz et al. 2025). We recently published an extended discussion of many measurement issues that may exaggerate the growth of religious “nones” (Conrad and Hackett 2026). In this short note, we highlight three common changes in the measurement of religious “nones” and call for survey and census organizations that make these changes to concurrently study how they affect the apparent prevalence of the “no religion” population.