Religious identification (BELIEVERS) by population size of the municipalities in Spain.

Previous research on religiosity in urban areas of Spain has typically relied on qualitative methods and focuses on densely populated provincial capitals. This study explores the significant variability in religious identification across Spain's municipalities, with individuals in larger municipalities reporting lower levels of religiosity than those in smaller ones. The study also examines how this variability is influenced by demographic factor such as gender, age, and education. The results reveal substantial differences in religiosity across municipalities, particularly among the eight Spanish municipalities with a population of over 400,000 residents aged 18 and older. Specifically, Barcelona and Palma de Mallorca show the lowest levels of religious identification, while Madrid falls in the middle and Murcia, Sevilla, Malaga, and Zaragoza show the highest levels. The data used in this study comes from a fusion of 125 monthly surveys conducted by CIS (Centro de Investigaciones Sociológicas) in Spain between January 2013 and June 2022 (excluding August), and includes 406,511 interviewees, 398,516 of whom identify as religious or non-religious. In summary, this study sheds light on the relationship between religiosity and population size in Spain, highlighting the need to consider this variable when conducting research in this field.