I wonder what’s going on in Mozambique with the large jump in congregations.
Reservations, I wonder why you think JWs will decline in 10 to 15 years when the “old guard” die off. Isn’t there always an “old guard” dying off? Why hasn’t there been a mass exodus today, or ten years ago, what the previous old guard died off?
The general idea that religion declines by generational cohorts is indeed supported by sociologists such as David Voas. (He’s got articles and a YouTube video on this topic)
If there was any generation that could represent the “old guard”, after which there would be decline, I would have guessed it would be the group that joined in the run up to 1975. But a large number of those will already have died. At least locally, a number of those that joined in the 1975 excitement have already died, and yet there hasn’t been a mass exodus so far. Many of their children, grandchildren, and even great grandchildren are still JWs.
Suggestions why JWs keep growing while other churches decline have included: their preaching activity and the threat of disfellowshipping.
I wonder if a bigger factor might not be JW rejection of higher education. There is good evidence to show that less educated people are more religious, as well as people who are economically precarious, which can accompany lack of eduction. Rejection of higher education is also a factor that makes JWs distinct from most other groups including Mormons, Adventists, mainstream churches and evangelicals.
In additional to lack of education being correlated to religiosity in general, there might be significant psychological factors at work too. Because it is a big decision for an adolescent JW to decide to comply with Watchtower pressure to abandon education at a crucial juncture. Having made that decision as a teenager probably weighs heavily on an individual for the rest of their life. A person might feel compelled to stick with the religion, while in other circumstances the might not have, in the coming decades in order to maintain psychological consistency with the decision not to pursue higher education as a teenager. Getting a job and married early probably cements other pressures to remain in the the religion too. So altogether I would argue that JW rejection of higher education might be one of the most significant factors producing comparatively higher growth for JWs than other religious groups. If Watchtower reversed its stance on higher education, or if young JWs started ignoring it en masse, that might be portentous of future decline.