Years earlier, when I was a freshman I think, I saw students protesting "The Klitgaard Report" to the president of Harvard, in which he noted the fact (it's a simple calculation) that African American students at Harvard had a lower GPA* than would be expected conditional on SAT scores. Brad DeLong, who actually read the report, says he detected no sign of racism in it.
Now obviously we all knew that average SAT scores of African Americans are lower than those of Euro-Americans (also known as honkies) so the SAT was presumably biased against African Americans (I mean if interpreted as a measure of smarts not assimilation in the dominant US cultural tradition). A justification for affirmative action which I personally liked a lot was that a reasonable prediction of performance would be standard measures (like the SAT) corrected for disadvantage. Thus I was most distressed by the Klitgaard report (not enough to go to the protest wehre Derek Bok talked to angry students as he often did because I mean he just did a simple calculation and the data ambushed him).
Now I understand. First lets assume that the cultural bias in Harvard grading is the same as the cultural bias in the SAT so race has the same effect on the expected value of the Harvard GPA as on the SAT score. Now note that an SAT score is the sum of the expected SAT score for that individual and a disturbance term which is specific to that test that day. The disturbance term includes did the student have a cold that day etc and also, if the student guessed on questions, did the student guess right. Fact is, if someone takes the SAT twice he or she will get different scores.
Given the fact that the distribution of SAT scores of African Americans is lower than that of Whites (first order stochastic dominance) if one has an African American and a White American with the same SAT score, one can rationally (and illegally) infer that the African American probably had a good day that day and the White American a bad day, that is that the expected value of the day specific disturbance is higher for the African American than for the White American.
Already this implies the Klitgaard effect even if the effect of race on expected SAT score and expected GPA is the same.
Of course that's not the half of it. Even without colds and lucky guesses and such, the SAT is correlated with GPA but they are not measuring the same thing (whatever it is and whether or not either has anything to do with one's real ability to contribute to the growth of human knowledge and the fullest flowering of humanity which they might because, hell, anything is possible). For example, in the SAT they gave us tiny little passages to read and it was wise to read every word. At Harvard professors don't bother to winnow their reading lists so you have to quickly decide what to skip and what to actually read (unless you are Brad DeLong and read 1000 words a minute and never learned that skill and is suffering from that lack now). So for the same SAT score, one would guess that the African American student has more ability to read every word and understand compared to his or her ability to decide what to read when he or she doesn't have time to read every word. Ergo** Klitgaard effect.
Now even if the SAT has a particularly strong cultural bias so race has a bigger effect on expected SAT score than on expected GPA, the measurement error statistical discrimination bit can imply Klitgaard's result if it outweighs the SAT is biased effect.
OK now sticking with GPA as our end point, I note that even if 11% of people who would get a harvard GPA over 3.9 (Harvard is different 4 is the max) are African American, this won't be true of people admitted to Harvard if 11% of admitted students are African American. It's that disadvantage and cultural difference and stuff makes the predictors of performance less accurate. Getting a student with an over 3.9 GPA requires that there be such a student and that one detects him or her and that you don't have to choose between him or her and the son of a super rich alumnus who will give tons of money if you admit his son but it is neither gross class bias or bribery because Harvard is different and superior and you don't understand and an institution struggling to get by with an endowment of only I don't know how much more than $ 40 billion*** has to make some compromises.
*Harvard called it something else like a "cube" because Harvard is superior and so it has a superior measure of grades)
** I never heard a Harvard student use that word except when denouncing "Ergo" a really dumb libertarian student magazine published by people who claimed some affiliation to MIT.