I do suspect this varies by HS. In ours, I think it is roughly half and half. As in roughly half of the kids going to Ivies or MIT, Stanford, Duke, or Chicago (that was how this study defined Ivy+) are either recruited athletes or legacies and such, the other half were not. It is hard to be sure because you would not always know who is a legacy, but the kids talk enough that I think that is at least roughly accurate. As always, I don’t think you can assume none of the legacies would have gotten admitted to an Ivy+ anyway, and indeed in some cases the kid is choosing between Ivy+ colleges where they were a legacy, and others where they were not–and they do not always choose the legacy colleges.
For what it is worth, it appears “HYPS” are notably tougher at our HS. MIT is sort of its own thing (usually it is one kid to MIT), but we definitely do not send someone to each of the HYPS schools each year, and I believe the average is right around 2 total for that group (although it is a could be 1, could be 3, sort of thing). For the other 5 Ivies though, I think the average is over 6 per year total, but with a lot more variability (probably because that is an overlapping pool with other Ivy+, some LACs, the military academies, and some of the top national publics). And most of the HYPS attendees were also admitted to other Ivies.
So roughly speaking, I think our admittance rates to Columbia, Penn, Dartmouth, Brown, and Cornell collectively are something like four times our admittance rates to HYPS collectively, give or take. Again, that’s a mix of recruited athletes and legacies and such, but also just non-recruited athletes who often get into multiple such colleges.
I’m pointing all this out just to note that things really do vary by HS. We’re not even one of the well-known Ivy feeders, and when I first learned about all this I was actually a little shocked how many kids ended up at whatever you want to call the most selective colleges that are not HYPSM. Again, recruited athletes and legacies is some of that, but really not all of it.