"Our new demographic analysis finds that affiliated women have more children than unaffiliated women − nearly a full child more per woman, on average, worldwide. In addition, the global median age of affiliated women is six years younger than unaffiliated women, so they have more potential years of childbearing and living ahead. We project these demographic characteristics will result in a more religiously affiliated global population in coming decades. Although current patterns of religious switching favor the unaffiliated, they are insufficient at the global level to offset the demographic advantages of the affiliated."
Background: People who are religiously unaffiliated (including self-identifying atheists and agnostics, as well as those who say their religion is "nothing in particular") made up 16.4% of the world's population in 2010. Unaffiliated populations have been growing in North America and Europe, leading some to expect that this group will grow as a share of the world's population. However, such forecasts overlook the impact of demographic factors, such as fertility and the large, aging unaffiliated population in Asia.
Objective: We project the future size of religiously affiliated and unaffiliated populations around the world.
Methods: We use multistate cohort-component methods to project the size of religiously affiliated and unaffiliated populations. Projection inputs such as religious composition, differential fertility, and age structure data, as well as religious switching patterns, are based on the best available census and survey data for each country. This research is based on an analysis of more than 2,500 data sources.
Results: Taking demographic factors into account, we project that the unaffiliated will make up 13.2% of the world’s population in 2050. The median age of religiously affiliated women is six years younger than unaffiliated women. The 2010-15 Total Fertility Rate for those with a religious affiliation is 2.59 children per woman, nearly a full child higher than the rate for the unaffiliated (1.65 children per woman).
Conclusions: The religiously unaffiliated are projected to decline as a share of the world's population in the decades ahead because their net growth through religious switching will be more than offset by higher childbearing among the younger affiliated population.
* Conrad Hackett, Marcin Stonawski, Michaela Potančoková, Brian J. Grim, and Vegard Skirbekk (2015). The future size of religiously affiliated and unaffiliated populations: Descriptive finding, Demographic Research, Volume 32, Article 27, pages 829-842. http://www.demographic-research.org/volumes/vol32/27/default.htm
Conrad Hackett - Pew Research Center, United States of America
Marcin Stonawski - International Institute for Applied Systems Analysis, Austria
Michaela Potančoková - International Institute for Applied Systems Analysis, Austria
Brian J. Grim - Boston University, United States of America
Vegard Skirbekk - Columbia University, United States of America