In regards to the Correlation vs Causation Argument, my guess would be that there is a bit of both. Certainly there is a selection bias towards more faithful Catholics in regards to attending the TLM. However, some things about the TLM do reinforce certain aspects of the Catholic Faith (for example the Real Presence in the Eucharist, the role of priests, the omnipotence of God and our relationship to him). With the NO these beliefs are watered down. Also the TLM transmits the idea that our Faith is not changed base on a whim or personal preference.
I am looking forward to the study which looks at the retention of the Faith of the adult childeren of those that attend the TLM vs. those that attend the NO. Even there I suspect the results will be mixed and hard to interpret.
My guess is that retention will be higher in the TLM than in the NO, but not as much as people might expect. Generally, attending a TLM (and the associatied orthodoxy of the priest) means that you can't lie to yourself about whether you really hold the Catholic Faith or not. Thus a child who grows up in the TLM and later rejects the faith will be honest about it and leave, whereas a child in the NO culture may keep going to Church as a cultural catholic, but as we see from the Pew poll, that doesn't mean they haven't left the Faith.
I do believe that if they Hierarchy would just admit they made a mistake and roll back some/most of the changes- that would bolster the Faith of both the TLM and NO attendees.
It would also lead to lukewarm catholics leaving in droves- but many have obviously left the Faith already, and their leaving would also bolster the Faith of those remaining. Unfortunately I suspect that the Hierarchy is worried most about the checkbooks that would leave with them.
