Recently there has been a spate of articles and other interest in the fact that Asians need a lot higher SAT scores, on average, to get into Harvard than whites. In effect, there seems to be a quota, about 15%, for Asian students. This is reminiscent of similar quotas for Jews a half century ago. If one looks at the population of students with the highest academic performance and test scores, there are a lot more Asians and Jews than their proportions in the US population.
Caltech, perhaps the only US university in this class that practices race blind admissions, has a student population that is about 40% Asian. Harvard claims 20% Asian for 2013, 12% African-American, and 13% Hispanic. Hillel, the Jewish student organization, says that 25% of the Harvard undergrads are Jewish. If we take all these statistics at face value, that leaves 30% for others, most of whom must be non-Hispanic, non-Jewish whites, who are consequently drastically under-represented compared to their proportion of the population.
One view of the problem is that the distribution of high achieving students is a lot different than the distribution of the overall population, with Asian and Jewish students being highly over-represented, whites somewhat under-represented and Hispanics and Blacks even more under-represented. If Harvard admitted purely on the basis of academic credentials, it would be mostly Asian and Jewish, with a large minority of non-Hispanic, non-Jewish whites, and hardly any Hispanics or Blacks.
Whether that is desirable is a question for Harvard, and perhaps the larger populace, to consider, but the point is that you can't be purely meritocratic and racially balanced.