I can't be sure, but there seems to be a relatively simple way to do that. Pick the lower bound on your definition of "top programs", and see what fraction of each cohort goes to a top program. If a program consistently sends 5 people to top programs, then you probably need to be in the top 5 of that program to achieve similar results. If that number varies a lot year by year, then there probably is no single number that sums it up.
It's not perfect but it's probably the best you can do with limited information asking a question like this. Barring the experience of someone who's actually attended one of these programs.