<p>NJres:</p>
<p>Apart from the reporter’s misuse of “yield”, I think it’s axiomatic for ED schools that (a) the average stats (and other quality measures) of the ED applicant pool are significantly better than those of the RD pool, but (b) the average stats of students admitted ED may be worse than those of students admitted RD, because (c) the acceptance or admission rate of ED students is higher. </p>
<p>That’s not illogical at all. Suppose a school rates all applicants on a 10-point scale, and accepts 5 ED and 25 RD applicants on the basis of rating (with ties broken by lottery) to get a class of 20. It gets 10 ED applications: 2 10s, 2 9s, 3 8s, 2 7s, 1 6, so the average is 8.2. It admits 5 (50%) students, with an average rating of 9.2, and defers the remaining 8s to the regular round. In the regular round, it has 100 new applicants and the 2 deferred: 12 10s, 12 9s, 23 8s, 30 7s, 20 6s, 5 5s, for an average of 7.7 among the new applicants. It accepts 25 students (25%), with an average of 9.4. The ED pool is better, but the ED acceptees have lower average stats, because the one (out of two overall) “8” admitted at the ED stage represented a greater portion of the ED admittee pool.</p>
<p>People will look at the overall stats, and say the ED kids were advantaged because they had almost twice the chance of being accepted than the RD kids – 50% vs. 25.5% (and really it’s 55% vs. 25%, taking into account the deferrals). If the ED kids are richer, that looks unfair. And, if you could accurately identify the “8s”, the difference is even more striking – the ED 8s were eight times more likely to be accepted, a 36% chance vs. a 4.3% chance. But for 78% of the applicants (84/110), ED or RD made no difference at all. All the 10s and 9s were going to get in, and none of the 7s or below. ED makes a difference for exactly 5% of the admitted class.</p>
<p>And the wealth effect of having ED overall is pretty minor. Assume (a) each of the ED applicants has wealth of $200, and each of the RD applicants has wealth of $100, and (b) the same kids would have applied, and the same yield achieved from the same kids, without ED. With ED, the expected average wealth of the admitted class is $125.26; without ED, it would be $118.75. That’s a whopping 5.5% difference, on pretty extreme assumptions about the wealth difference in the pools. </p>
<p>Now, look what happens if I change the (somewhat over-optimistic) yield assumption, and assume instead that without ED the college would have to admit 33 applicants (i.e., 3 more) to get a class of 20, and that the same kids wouldn’t necessarily enroll without ED. Then, the average rating of the accepted group would go down from 9.4 to 9.27, the average rating for the enrolled class would go down from 9.38 to 8.7, and the average wealth would go down to $112.88. </p>
<p>So the college might reasonably believe it faces the following tradeoff: By eliminating ED, it could lower the average wealth of its class by 5-10%, at the risk of lowering its average rating by 0.7. I don’t know that is a compelling case to eliminate ED.</p>
<p>My illustration is simplified but not, I think, unrealistic. It suggests there is less to the whole ED tempest than may otherwise appear.</p>