Information on religious affiliation for the total population is available from 1951 to 2001 in the form of self-declaration from the censuses. Since the censuses changed to a register-based survey, data on this characteristic is no longer collected within the framework of the census. In 2021, Statistics Austria conducted a voluntary survey on “Religious affiliation of the population in private households” on behalf of the Federal Chancellery, which, after estimating the religious affiliation of the institutional population, supplements the time series since 1951.
In addition, Statistics Austria records the number of withdrawals as well as admissions and readmissions among the religious communities in Austria that are subject to church contributions (Roman Catholic, Protestant – Augsburg Confession and Helvetian Confession, Old Catholic). These statistics on changes of religion are based on a survey of the religious communities and are available as a time series from 2001 and also for the federal provinces from 2011.