As with any other group tracked by Federal guidelines for identification of race and ethnicity, self-identified ones.
As a group, asians outscore whites on standardized academic exams. Whites in turn outscore blacks. See a recent SAT composite summary here, in the bottom table:
Asians: 1654
Whites: 1576
Blacks: 1277
At the top tiers of performance, the differences become quite stark, with very very few high-performing blacks on standardized exams.
“Almost No Blacks Among the Top Scorers
on the Scholastic Assessment Test
It is important to explain how the SAT racial scoring gap challenges affirmative action policies at the nation’s highest-ranked colleges and universities. Under the SAT scoring system, most non-minority students hoping to qualify for admission to any of the nation’s 25 highest-ranked universities and 25 highest-ranked liberal arts colleges need to score at least 700 on each portion of the SAT…
Let’s be more specific about the SAT racial gap among high-scoring applicants. In 2005, 153,132 African Americans took the SAT test. They made up 10.4 percent of all SAT test takers. But only 1,132 African-American college-bound students scored 700 or above on the math SAT and only 1,205 scored at least 700 on the verbal SAT. Nationally, more than 100,000 students of all races scored 700 or above on the math SAT and 78,025 students scored 700 or above on the verbal SAT. Thus, in this top-scoring category of all SAT test takers, blacks made up only 1.1 percent of the students scoring 700 or higher on the math test and only 1.5 percent of the students scoring 700 or higher on the verbal SAT.”
With all groups, the highest scores generally come from reasonably privileged backgrounds, and so socioeconomic status generally trends with academic performance. This means schools cannot simply achieve diversity by taking into account privilege. At every tier of privilege, asians still substantially beat out their equally-privileged peers.
If a school used a pure merit-based system (adjusted for socioeconomic privilege), asians would be even more hugely over-represented than they are now. This is exactly the problem Ivy Leagues are facing. There are plenty of high-scoring asians to fill the classes, and a paucity of high-scoring blacks. Every institution must set de facto “diversity” criteria that have the effect of not accepting asians who would be readily admitted were they blacks with the same set of scores and “other” skills.