The first thing that comes to mind is, if you don't have a high level of trust in the society, the trust fostered by being the same religion is all the more va

The first thing that comes to mind is, if you don't have a high level of trust in the society, the trust fostered by being the same religion is all the more valuable. If you think you can go out into a high-trust society and do just fine, then leaving that religious community your parents raised you in seems low-cost. Also, if high trust drives economic growth, and wealthier societies become less religious, you would get that same pattern. I think to determine which is driving which, you would need to look at the relation between religion now and trust levels in the past, and vice versa.