There are a handful of modern religious and fundamentalist groups that sociologists study for this purpose: Mormons, ultra-orthodox Jews, evangelicals, etc.
The interesting thing about these groups is that they exhibit “carrying limits”: they get to particular community sizes and begin to experience attrition through secularization.
The interesting thing about these groups is that they exhibit “carrying limits”: they get to particular community sizes and begin to experience attrition through secularization.