Abstract
The article examines the relationship between religiosity and demographic behavior in the United States, Europe, and Russia using Christianity as a case study. The relevance of the study is determined by the transformation of religious institutions, changes in family values, and declining fertility rates in a number of developed societies. The aim of the article is to identify how religious affiliation, religious practice, and the institutional influence of religion are associated with fertility rates and family behavior in different regional contexts. The study compares the approaches of P. Jenkins, D. Voas, N. Peri-Rotem, K. McQuillan, A. Adsera, and other scholars, and also uses open demographic and sociological data from international research centers. It is shown that the influence of religiosity on fertility is not universal: in the United States, religion continues to play a significant role in family behavior; in Europe, its influence is manifested primarily among practicing believers; while in Russia, the growth of nominal religiosity does not lead to a direct increase in demographic indicators. The article concludes that, when analyzing demographic processes, it is necessary to distinguish between nominal religious identity, regular religious practice, and the institutional role of religion.