Might be able to get that data from the Harvard lawsuit eventually.
Anyway, Williams’ class is less than 1/3 the size of Chicago’s, I think it has more varsity sports teams (yes: just checked, 30 vs. 18), and it admits less than half of its class ED (vs. 70%+ at Chicago). Even with relatively few pure recruits, the percentage of athletic recruits in Williams’ ED acceptance pool is going to be way higher than the percentage of athletic recruits in Chicago’s ED pool.
Williams accepts about 250 kids ED. If 100 of them are recruited athletes – which would be fairly low – that’s still 40% of the ED acceptances. Chicago accepted about 1,300 kids ED this year. If 200 of them were recruited athletes – and that seems way high for Chicago; that’s Ivy numbers for colleges with many more teams – it would still be only 15% of the ED acceptances. The effect of athletic recruiting on Williams’ ED numbers is meaningful. (Just not all the way to “eliminating the difference between ED and RD”; they would have to be recruiting Ivy numbers to do that, and they don’t.) The effect of athletic recruiting on Chicago’s numbers is a lot less.
ED1 and ED2 having the same rate: is there anything different about the applicant pools that would point toward choosing ED1 vs waiting and applying ED2, for some particular type of student (excluding an athlete applicant)?
Are ED1 deferrals only punted to RD or are they ever reviewed during ED2?
ED1 is deferred to RD. ED2 is waitlisted. That’s one difference.
If you know that UChicago is your first choice you should apply ED1. The admit rates above are only an educated guess.
One could assume that the ED2 pool would be stronger as it would collect applicants who are deferred from the SCEA/REA schools.
^^ This is true. S19 is a much stronger candidate than his older sis (which is saying a lot). He’s set on an SCEA/REA school due to a special program that he’s particularly drawn to. But UChicago is also up there and if they had the same program it would be no question he’d apply EDI. He’d be delighted with either school but his SCEA/REA has the edge. We are very glad about EDII because this way he has two early opportunities at two amazing institutions. By the way, S19 told me he’ll be sending along the EDII app. as soon as he’s deferred from the other school so he has no delusions about his chances there. UChicago would be happy to get him (IMHO 
) and he’d thrive there.
“One could assume that the ED2 pool would be stronger as it would collect applicants who are deferred from the SCEA/REA schools.”
Do we know students who think they can get into SCEA school but don’t are stronger?
Also, ED2 will be collecting students who applied to SCEA school strategically because they weren’t sure of getting into Chicago itself ED1, so as to get two stronger chances at a top-3 school.
And students who applied EA to Chicago with hopes of getting some merit money later but who didn’t get into Chicago EA.
We can tell individual anecdotes. My DD had legacy at Chicago and at a top-3 SCEA school, perfect scores on the old SAT, tons of AP classes, 4.0 unweighted, very high class rank, good AP scores and SAT subject scores, interesting extracurriculars that she was sincerely deeply engaged in, multiple national awards, and very good essays. The combination of legacy at the top-3 SCEA school, her stats, and her awards made her a very likely SCEA admit to the legacy SCEA school. The combination of her stats, her awards, her extracurriculars, and the high school she comes from (region and type) made her a likely SCEA admit to a different top-3 SCEA school (based on history at our high school). She could easily applied to one of those schools SCEA and waited for ED2 at Chicago, but she didn’t. We thought about her applying EA to Chicago for a chance at merit money from them and a chance at full merit scholarships at some top 20 universities and LACs, but since Chicago was the school of choice and their merit money had seemingly been decreasing lately (and wasn’t that huge anyway), and DD didn’t really want to be making her college decision in April and not get her pick of dorms at Chicago, she decided to apply ED1 to Chicago. Very happy there.
So that’s one anecdote. But in the end, I don’t know how to guess what the average ED1 student versus the average ED2 student is like. The assumption that students who apply to the SCEA schools SCEA are “stronger” is perhaps questionable. The idea that students who apply to the SCEA schools SCEA and don’t get in are stronger than those who know they want to go to Chicago and so apply ED1 seems to me even more questionable. Chicago certainly admits very strong students, as judged by their standardized test scores.
EDI has the potential to trade on “quality” a bit. According to Nondorf, UChicago has only continued to see ever-stronger classes with each passing year, but the proper measure is what would the class have looked like w/o layering in a binding admission plan. All this is splitting hairs, but an argument can be made that if your Plan A is an SCEA/REA and your Plan B is a binding plan, then you are revealed to think you are a stronger candidate than someone who applied EDI. The rationale is that you believed you would have been accepted binding, so you use that as a “backup” and choose something more competitive for cashing in that early chit.
However, that’s only one type of applicant in the EDII pool. There are also those students who would have applied EDI except they needed a GPA-boost from first half of senior year in order to make their applications a bit more competitive. They are going to be no more competitive than other EDI’s, and perhaps even a bit less.
Finally, there are those who, like my kid, applied EA, were deferred, then switched their apps to EDII. They can really be all over the place in terms of quality - some will resemble EDI, others will not.
It’s very hard to determine “average quality” from these three pools because we don’t know the mix. Guessing UChicago doesn’t worry about it so much; their job is to select the best fits from each pool. The going assumption on CC is that the EDII pool is packed with SCEA-deferreds but we really don’t know that one way or the other.
However, one factor might tip the scales to EDII being a tad higher quality than EDI: EDII doesn’t get deferred. If you aren’t accepted you are waitlisted. It’s like a binding regular more than an “early”. So if you are applying EDII for the first time - or even if you were deferred - you might be pretty confident that you’ll be accepted since it’s your 1) “backup” and 2) the stakes are high w/no rollover to Regular admission. However, there might also be an expectation that UChicago would trade a bit on quality (it’s a binding plan, after all) so it’s worth it for you to “go for it” since you wouldn’t have made it in the regular round. So maybe it can go either way and again depends on the “mix” of expectations in the EDII pool.
“There are also those students who would have applied EDI except they needed a GPA-boost from first half of senior year in order to make their applications a bit more competitive. They are going to be no more competitive than other EDI’s, and perhaps even a bit less.” Or needed to take the SAT/ACT again.
You also have to remember that UChicago is not the only top school to offer ED2, Vanderbilt and a number of top LAC’s offer ED2. Given that, a logical choice for most (in this competitive environment) is to have two early admissions cycles for applications. Of course, if UChicago is your first choice then ED1 would be the way to go (no matter how strong of an applicant you are) with possibly ED 2 at other institutions. Bottom line is ED 1 at UChicago signals a clear first choice and that means something. ED 2 signals a close second or even a first choice but most will have applied early somewhere else and were deferred (I’ll leave out rejected since that would mean they weren’t competitive at all). Again you can’t be absolutely sure but a logical conclusion would be that many strong deferred applicant who might have been accepted in the RD round look at the acceptance rates and decide to apply ED2 to another school that they would be just as happy at (or very close to it).
IMO, the ED2 rounds are to designed by these schools to do exactly that, pull in strong candidates who have a strong interest in the school but wanted to try somewhere else first (mostly at SCEA/REA schools).
The main reason UChicago offers ED2 is likely to be the same reason that it offers ED1. It wants to know who is considering UChicago as “first choice” in that admission round. How you got there is probably not important in the least.
My son’s thinking is very likely not unique among ED2 candidates, but he really loves the option, because this way he doesn’t have to agonize over two world-renowned, great-fit schools. I think he’s planning to let the Fates intervene. If the Fates happen to bump him down to #3 - 5, he’d still be pretty happy but it wouldn’t be quite the same as the first two. (NB: they are ALL excellent schools and he’d do well at any of them - even his safeties).
@JBStillFlying well I am interested in where your son ends up, I definitely think it’s harder for males in admissions.
“I definitely think it’s harder for males in admissions.” Curious why you say this.
^^ For the past couple of years the admission stats at UChicago have favored the guys. Just because more gals apply and it appears they try to keep the class at 50/50.
Actually I’m talking about all the top schools, I just think that in society in the U.S, the opportunities for boys is still greater than it is for girls leading to males having stronger applications and therefore being a more competitive group as a whole.
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S19 might have one advantage: his prospective major needs more guys 
:-bd
@JBStillFlying , you make an interesting suggestion. It’s one I have never thought of as applicable to the University of Chicago - that boys may actually be getting some form of AA, both in general (in order to achieve a balance of the sexes at a school where the women applicants exceed the men) and in particular programs (where men are underrepresented).
I am not entirely convinced on either score, but it’s a provocative thought. I believe the split overall in the student body of the College favors men 52-48. If this gender engineering were going on, one wonders why the split wouldn’t have been more perfectly equal or even tilted slightly the other direction. We know boys are in general not doing so well in school these days, but is that true of the subset of them who apply to a place like the U of C with any chance of being accepted? There is a pretty fat tail of talented boys - just as of talented girls. At these levels I speculate that there is probably little difference in quality between them. And, notoriously, boys, with all the woeful statistics favoring them as candidates for incarceration, madness and cognitive disorders, continue to be overrepresented in the very highest categories of achievement, especially STEM. Surely that makes them equally competitive with girls at a place like Chicago where almost every plausible applicant is a statistical outlier.
I have noted, however, the rather drastic decline of boys entering the Humanities. Would that give an avowedly poetry-mad or Shakespeare-spouting boy an edge? Seems plausible. Of course nobody declares a major on the application, and there are plenty of changes of orientation as kids work through the Core and encounter previously unknown possibilities (or failures of interest or competitiveness in the ones they brought with them). Two of my friends who started in math ended up in English, seduced by the siren song of expressive language. So those considerations make me skeptical of the proposition that guys with these early interests are being scouted out and given an advantage at the outset. Yet, if the ultimately very big imbalance between the sexes in the Humanities is to be believed, a real sea-change seems to be going on with the interests of guys at the college level. Is it possible that schools and departments regard this as a problem that needs to be corrected, and admissions officers take it into account? Could be.
I think it’s almost a given at any top-level liberal arts university or college that a boy who looks like he will probably major in French literature or history of art gets some marginal advantage for that, just as a girl would who showed a high degree of interest and achievement in math or physics. (I’m talking here about something significantly beyond doing well in AP Calculus BC or AP Physics C. I think there are a lot more girls than there used to be interested in those fields, but still enough of an imbalance to warrant a boost.)
At this point, there’s almost certainly some advantage for any student who looks committed to hard-core humanities. The fancy universities care about those areas, and have huge investment in them. They don’t want to have a situation where their 8-10 tenured Classics professors have no undergraduates to whom to teach advanced courses. And they also don’t want to have female departments and male departments. I’m not suggesting that they will reach down and admit underqualified boys who like poetry. It’s more that they reject fewer highly qualified boys who like poetry compared to highly qualified girls who like poetry.