profdad, you’re right that it’s harder for the students than it is for us; they’re students, and we’re professionals. I apologize for implying equivalence. My point was only that it’s not easy for us to defer people, either. I think sometimes people think that it’s easier for us to just defer someone than deny them, but it’s actually the reverse: it would be much easier for us, workload-wise, to deny many more students in early, but we would be doing MIT (and the applicants) a disservice.
As a point of clarification: the statistics you requested are available here - http://mitadmissions.org/apply/process/stats, and the deferred instructions blog post was posted, as is our convention, two days after decisions here: http://mitadmissions.org/blogs/entry/tips-for-the-ea-deferred
The “applications evolve” explanation is the correct one, but the problem is that there is so much uncertainty about which applications will evolve how. Here are a few examples, made up completely on the spot by me, right now, because I woke up early and have no life, but representative of archetypes we see:
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a student that we want to admit early but who comes from an underresourced high school and this is her first time taking AP STEM classes. By EA we don’t have any grades on her yet and we want to make sure that she’s doing well as she steps up to the rigor of APBC and AP Phys, so we defer her because her reaction to that academic challenge could go either way and we need more information
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a student who applies early having just begun a research project. The research supplement sounds promising and the research LOR is going gaga but so do the portfolios/LORs for many of our students. The student indicates she is submitting her research project to, say, the Regeneron STS and will be notified about her semifinalist or finalist status in January or February. We defer to RA to see if the student is vetted by experienced judges as performing research that is among the top 300/40/10/1 of their cohort.
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a student who is (to use the CC term) “unhooked” (i.e., lacks a formal distinction that identifies them as a clear institutional priority), but much beloved by their community and might play the same role at MIT. We don’t have the space for them in early, and we don’t know what the pool will look like in regular, so we defer to regular to see how many spaces we have and if we have the room to allocate to a student who lacks formal distinctions but remains compelling for fuzzier but still powerful reasons.
As you can see from these three (I emphasize again arbitrary/made up/any resemblance to applicants past or present is completely accidental) examples, there are different kinds of evolution here. Some, like the grades, are largely within the applicant’s locus of control. Some, like the research contests, are mixed between them and the external program that they work with which vets, verifies, and fetes their projects. Some depend entirely on us and our process and are outside the locus of control of the students. This is why we can’t give ‘reasons’ for a deferral. Often, there’s nothing ‘wrong’ with an application, at least in the sense of anything they can fix; instead, it’s stuff outside of them which nonetheless overdetermines their outcome in the process.
So the deferral period is a time during which these uncertainties, distributed across many different actors/agencies, are moving from flux to equilibrium, until sometime in March when we have to finalize decisions and so at that time we take a look at the students and say “allright, these are the students who were deferred, and here’s how all of these things worked out, and now here are the best decisions we can make at this point.” And the result of that, obviously, is that most students we deferred were denied anyway, because our applicant pool is ludicrously deep and strong. But again, we didn’t know which students those would be in early, or we would have denied them in early.
For us to deny more students than we currently do in early, we would have to make decisions with known-to-be-incomplete-information, decisions we couldn’t take back, and decisions that would potentially impoverish MIT (and also turn away really great students who might, on balance, have preferred to been deferred if they might have gotten in). So what we try to do is to deny as many students as possible in early, but only if we are effectively certain that they will not be admitted in regular.
It’s hard. And as someone who went to my undergrad off the waitlist (aka RA deferral), I get the gut feels. I’m just trying to explain the background mechanics that “applicants evolve” is shorthand for.