@StevensPR RD yield cannot be greatly manipulated through waitlists. Also how are you so sure that Hopkins does not engage in student profile refinement as you call it? Every schools does that, but still this can only go so far. You cannot predict what choices an RD applicant will have and you cannot predict which applicants will for sure choose your school of admitted. Chicago’s yield has increased because it has managed to maintain a top 10 USNews spot for quite some time now, it is generally high ranked, and has revamped its undergrad to attract a wider audience. Still Chicago is a more niche place relative to the ivies so it tends to be a bit more self-selected. RD yield is not at all as easily manipulated as you make it to be.
Why is Parchment garbage? It is not 100% accurate but they jut track revealed preference. there are no 100% accurate verifiable sources for these sort of things anyway.
The difference is RD yield between Hopkins and Cornell/Brown, the other Ivies is not due to the fact that these schools have some amazing yield protection techniques that somehow Hopkins doesn’t use.