During winter break my ds friend told us his mt uarts class started out with 60 and after two years is now down to @35. Students have left for national tours, broadway, other schools, $$ reasons, homesick, etc. I would find it hard to believe that all schools do not have the same kind of movement but maybe in smaller numbers. My d is a freshmen vp but her class started with 18 and she is now at 13. At the beginning of the school year 2 left/did not show up due to finances, one left due to serious family emergency and 2 changed majors after first semester. The same thing has happened with her mt roommates class. I don’t have those numbers.
I agree with the notion that this is a natural process not unlike other majors. It would appear that all programs have movement. Some years will have exceptional retention rates and some will not. I would wager it’s as much student related and not necessarily reflective of the school/program. I would also wager that transfers out due to fit or program quality are more rare when talking about the schools discussed on this forum. No quantitative data but what in the arts is:)