Marriage generally seems to be something that devoutly religious people are simply better at, and that alone might be why our average fertility is higher.
Discussion
Or maybe religious people tend to stay in toxic marriage longer because of reliagious reasons..
People who are good at commitment turn out to be good at commitment.
I would like to think there is a causal relationship as well, but it would be interesting to compare to something like Lions Club membership.
While I don't think that statistic is available, it is kind of funny that it can be approximated by a chart you posted earlier. If we consider devout Protestants as directionally secular commitments with respect to devout Catholics we do see a causal relationship.
