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.