Merging the Religious Congregations and Membership Studies: A Data File for Documenting American Religious Change

The decennial religious congregations and membership studies are a popular data source for analyzing local religious composition and diversity, but several methodological challenges hinder merging the datasets for longitudinal analyses. In this paper, we introduce strategies for addressing four of the most serious challenges: religious mergers and schisms, changes in membership standards within certain groups, missing data and changes in county boundaries. In doing so we successfully merge the 1980, 1990, 2000 and 2010 collections and build new longitudinal datasets of congregational and membership counts at the state and county levels. These changes increase religious group representation from 48 to 76, reduce bias from missing data, allow for the more reliable inclusion of 20–23 million adherents in each year, and improve overall ease of use. We also document instances when corrections were not possible and alert readers to the limitations of the merged files when measuring change among certain groups. The new longitudinal files are accessible from theARDA.com.