I suspect that HYPS do more athletic recruiting and have more legacy applicants than Chicago does and I know that both groups are disproportionately represented in their SCEA pools. The factors that make those candidates particularly attractive to their SCEA school (legacy, most obviously) don’t necessarily make them the strongest candidates for other schools.
Chicago, like MIT, gets two waves of especially strong candidates. The first wave are kids who prefer Chicago to HYPS despite the fact that they would have an excellent shot at admission to one or more of those schools. Such kids do already forego something (the benefit of SCEA at their second choice/harder to get into school) in order to apply EA to Chicago.
The second group is kids for whom Chicago was a genuine second choice and who were not successful in the SCEA or ED round. The strongest of these applicants will probably have been deferred to RD rather than rejected outright by their first choice school, so there’s no reason to assume they’ll choose EDII. Most are likely to remain RD candidates for Chicago.
Maybe it’s just my particular vantage point (former professor, kid in East Coast private school, alumn of 2 HYPS schools, interviewer for one of them), but the assumption that many posters seem to be making that the kids who apply EA to Chicago are generally weaker than the kids in the SCEA pools strikes me as just plain wrong. So many kids see HYPS as lottery schools (and golden tickets) and think that their odds of getting in are much higher if they apply SCEA. So these schools get applications from folks who don’t have a chance in hell of getting in. They’re not unqualified, but there’s nothing that makes them stand out in any way from thousands of other applicants.
By contrast, Chicago is known as a school that’s really demanding. The Uncommon Essays immediately reinforce that impression. You can’t count on random strangers (or your parents’ friends) to be wildly impressed if you get in. And EA at Chicago doesn’t appear to offer the same kind of boost that ED or SCEA elsewhere does. So, basically, almost the only reason to apply EA to Chicago is that you really want to go to Chicago. (The other reason may be to give you a second shot at a high-ranking school if the ED bet you’ve placed elsewhere doesn’t work out. As I said before, if I were going to tweak the current system, I’d shut that option down.) The Chicago EA kids from my daughter’s school were a smaller group than the SCEA kids and they would have been among the top SCEA candidates had they chosen that route. Like MIT, there’s some serious self-selection going on among kids/families in the know. In the environments I’m in, almost everybody wants HYPS. But only very smart kids who love to read/think/talk/experiment, who want to be challenged and who expect College to involve hard work start out wanting to go to Chicago or MIT.
I recognize that I’m coming from a particular class/occupational/geographical fragment and that it shapes my perception. But since we are talking full pay, the demographic I’m referring to is highly relevant. In general, I think that in recent years U of C has been quite successful at (and should continue) getting the word out about what kind of place the university is and the distinctive culture it has to offer. As someone who went to college at a university that was considered grad school-focussed (and then to grad school at a university that was considered undergrad-focussed) and then taught at a university whose history is quite similar to Chicago’s (the college was something of an afterthought ), I’ve seen, from a variety of perspectives, that there are kids out there (from every demographic) who are looking for and would thrive in a college environment where the academics are central and where cutting edge research is being done. I also know that these kids aren’t the norm – even at prestigious universities with highly selective undergraduate admissions. The focus should be on finding such students and convincing them that Chicago is the place they want to be.