Volume 32 - Article 27 | Pages 829–842  

The future size of religiously affiliated and unaffiliated populations

By Conrad Hackett, Marcin Jan Stonawski, Michaela Potančoková, Brian J. Grim, Vegard Skirbekk

Response Letters

Most recent first

07 January 2017 | Response Letter

Response: Modeling religious switching as a young adult phenomenon

by Conrad Hackett

Responding to our article on the future size of religiously affiliated and unaffiliated populations, Pearce Aurigemma suggests it is appropriate to model religious switching primarily as a young adult phenomenon and asks whether we do so. The short answer is yes, we model religious switching as a phenomenon occurring between ages 15 and 29. A longer explanation of our rationale and procedure is below.

Studies of religious switching indicate that this phenomenon is often concentrated in young adult years, roughly between ages 15 and 29. Change in religious affiliation may occur as young adults move away from their parents and partner with someone of a different affiliation status. While some religious switching may take place at other ages, switching is modeled as a life course phenomenon in which some young adults change their religious affiliation status. There may be some time periods during which people of all ages are prone to religious switching, such as when political circumstances in a country encourage or discourage religious identity or lack of religious identity. Our models do not attempt to include such period effects.

The typical procedure for measuring religious switching is to compare the religion in which a person grew up with their current religion (when the person is an adult). The best sources of data on religious switching are nationally representative surveys that ask adults about their current religion as well as the religion in which they were raised. In 70 countries, data are available on both the religious upbringing of survey respondents and on current adult religious identity. These surveys typically have sample sizes between 1,000 and 3,000 respondents. Data sources include cross-national surveys carried out as part of the International Social Survey Program and by the Pew Research Center, as well as some surveys carried out only in one country. Unfortunately, while censuses and large-scale demographic surveys often measure current religious affiliation, they generally do not measure religious origins, and so they cannot be used to directly measure religious switching.  

Since men and women often follow different switching patterns, we calculated rates of switching separately for men and women based on the experiences of adults ages 18-54 at the time of the survey. We assume that the experience of young respondents is the best source of information about likely switching patterns for emerging generations, so the experiences of older respondents (those ages 55 and above) are excluded from the analysis. Our analysis was initially restricted to the switching experience of 30- to 54-year-olds; while this restriction allowed the focus to be on respondents who have recently completed their young adult years, it left less-than-optimal sample sizes. Including the full range of adults ages 18-54 in the sample increased sample sizes and did not appear to compromise the reliability of the switching rates.

In countries for which switching data are available, we generated recent rates of switching. The main projection model assumes that emerging cohorts will switch from their childhood status at the same rate observed in recent survey data. Switching rates are applied to rising cohorts of 10- to 14-year-olds at three intervals (the transition to ages 15-19, to ages 20-24 and to ages 25-29). For example, if a survey indicated 87.5% of adults who grew up affiliated are now unaffiliated, this rate of disaffiliation would be modeled for a cohort in three steps by switching 50% of affiliated people to unaffiliated status at each of three five-year steps. With 1,000 affiliated 10- to 14-year-olds at the first step, 50% disaffiliation in five years leaves 500 affiliated 15- to 19-year-olds. In the next five years, 50% disaffiliation leaves 250 affiliated 20- to 24-year olds. In the final step, 50% disaffiliation leaves 125 affiliated 25- to 29-year-olds (87.5% of the original 1,000 children have disaffiliated). Such high rates of disaffiliation are not common and are used here only for ease of explanation.

The model takes into account recent patterns of switching from affiliated to unaffiliated status as well as from unaffiliated to affiliated status. To varying degrees in each country, these patterns can offset one another. For projection purposes, each person was allowed one switch, which is all that is directly measured in the surveys this method draws upon. Though this does not fully capture the complexity of individual religious identity and switching, it captures aggregate patterns of change.

More details about the methodology of our full study are available at: http://www.pewforum.org/2015/04/02/appendix-a-methodology-2/.

20 December 2016 | Response Letter

Question: Distribution by age of transitions

by Pearce Aurigemma

Anecdotally, it would seem that 15-30 age range would be the highest age range to transition from religiously affiliated to unaffiliated. And the largest group 28% age 0-14 are religiously affiliated. 

Do the calculations take into consideration a higher transition before average fertility age? It seems possible if transitions happen at a significantly higher rate before fertility age the conclusion could land the opposite direction.

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