Religion and fertility – A longitudinal register study examining differences by sex, parity, partner’s religion, and religious conversion in Finland

We use longitudinal data on fertility and religious affiliation in Finland to examine average number of children and parity. All analyses are based on detailed information from the Finnish national register of each person’s religious denomination for men and women born between 1956-1975. We identify higher fertility among members of the Evangelical Lutheran state church and other Protestant churches, and lower fertility among individuals with no religious affiliation. Most other religious groups—Orthodox Christians, Jews, Muslims, and adherents of Eastern religions—have intermediate levels of fertility. We also find that religious converts typically show a pattern similar to that of co-religious non-converts of the group they convert to, though with even more distinct deviations from the average patterns. Women show larger differences by religious affiliation than men. Fertility differences by religion are particularly pronounced for childlessness. Overall, differences between religious groups are rather modest, and childbearing patterns are quite similar. Our results provide, to our knowledge, the first examination of religion and fertility using national-level longitudinal data.