Hard to argue with the Harvard litigation data on the advantage of SCEA there. I suspect YPS might yield similar results. I would say though that what the data might not account for are certain subjective factors, especially in the EC’s and essays, that might make the SCEA candidates a better fit in Harvard’s eyes. The final decision was not based on which X number of kids had the highest combination of scores, but still involved subjective debate of all those who made it to that cut. You would think that a vast majority of SCEA applicants for H (and YPS) have that school as their personal top choice and their essays and how they portray their EC’s in their essays are more finely crafted and tailored to H (or YPS) than the average also highly qualified RD applicant. Speculation on my part, and from a sample size of 1, S wrote more finely tuned essays for his SCEA school than others, some of which were derivative to his SCEA essays when the subject matters overlapped. I don’t think he is unique. Can’t fully test my theory because he saved me application bucks by dropping his other apps after he got in.
What I find most problematical are parents/kids who are working the problem backwards. That is they have a list of 15 ± highly selective schools and are trying to game which is the most highly ranked (by prestige, not their own fit) school the ED (esp) or SCEA card will be the most advantageous for them based on published admit rates between ED, ED2, EA and RD rather than ranking the schools by personal fit and then determining if applying the ED/EA card for one of their top picks is worth it. The other rookie mistake is ascribing a greater value to ED than it is worth based on hope (like assuming 20 local EC’s will make up for below average academics – oftentimes the same people). The ED/EA boost is for the qualified candidate who is right on the fence – the one who makes it to Committee in the first place imo.