Sparkly – most means more than half, so even if Joseph is right that most OTD’s come back, there might still be many that don’t.
Also, I assume that Joseph is referring to people who are now in their teens and 20’s. People in their 40’s were from a different generation (that was before OTD became “a thing”) so things might have been different, and the reasons why people went off and whether or not they came back might have been different.
The whole kids-at-risk/OTD phenomenon of today only started app. 20 years ago or less, so most of the kids who were part of that phenomenon are now 30-35 at the most.
In any case, I think it’s true that a lot come back but I don’t know if it’s most or not. It is probably a much larger percentage than the percentage of not-Frum people who end up becoming bt’s which is a comforting thought. It means that their education was not a waste! And that whatever complaints people might have about the Yeshiva system, it’s doing a very good job, since even those who go off (which is a minority to begin with) are more likely to end up Frum than people who do not have a Yeshiva education.