This matrix is dynamite: it shows how people in the USA changed their religious affiliation after age 16 and what they had moved to as adults (from Skirbekk, Kaufmann & Goujon, p.300). It uses General Social Survey (GSS) data so the classification divides Protestants into categories including “Fundamentalist” (PFU) and “Protestant Moderate” (PMO), which I have highlighted on the table.
Notice in “Net Flow” that “Protestant Moderates” are positive +10.3 – these churches are attractive to outsiders. People who grew up in other affiliations (or secular) are joining them. The denominations in this category include Episcopalians, most Lutherans, some Methodists and Baptists, and “Open” Evangelicals.
Observe by contrast that “Protestant Fundamentalists” have negative -3.3 net flow on the transition matrix – those churches are comparatively unattractive to outsiders. The FPU category includes (as far as I can tell from GSS Methodological Report 43) the Missouri Synod Lutherans, many Pentecostals, and “Conservative” Evangelicals.
Despite this, overall the Fundamentalist churches are still growing numerically. Why is this? The same article (Skirbekk, Kaufmann and Goujon p.298) found that “Fundamentalist Protestants” had a Total Fertility Rate (TFR) significantly higher than the national average. So although they “lose” a larger proportion of their kids, they have more to start with.
It looks like “Fundamentalist” Protestants are doing badly at attracting outsiders. I’ve read their books, heard their audiovisual broadcasts preaching pronatalism, telling their congregations to have more kids. It sounds like they are relying on the statistical likelihood that if they bear a larger number of children some when adult will stay and follow their parents’ religion. Professor Danny Akin (a Southern Baptist) advised “if you have one child as opposed to four, five or six, then you have a much smaller initial mission field” (interview by Trevin Wax, 2009).
This is a worrying trend because there are many cases in history of religious groups that began as outgoing and open, but decades or centuries later turned inward and start relying on children to perpetuate the institution. Think of the Hutterites and the Amish; not many outsiders joining them today. It’s a recurring temptation for churches to transform themselves into ethnic groups. It’s not really easier, in fact its hard labour (pun intended), but apparently it looks like a dependable human strategy to the new pronatalists. They seem to “put confidence in the flesh” (Philippians 3:4-5) – the pronatalists should instead consider that the Holy Spirit reaches out to whoever He will regardless of ancestry and parentage. And that high birth rates are incompatible with increasing longevity and maintaining quality of life within ecological limits.