On 9 October 2012, by coincidence the same day that Mismatch hit the bookstores, the IZA Journal of Labor Economics published "What happens after enrollment? An analysis of the time path of racial differences in GPA and major choice." This study of Duke University students carried out by three Duke professors--economists Peter Arcidiacono and Estaban Aucejo and sociologist Ken Spenner--provides further evidence to support Sander and Taylor's argument. It tracked two classes of Duke undergraduates in all fields of the schools of arts and sciences and of engineering--a total of 1563 students--over the 4 years of their collegiate careers. It found "dramatic shifts by black students from initial interest in the natural sciences, engineering and economics to majors in the humanities and social sciences."
But, the authors show, that is not how things work out for many minority students. At the start of their Duke careers, black students generally receive lower grades than whites. The grade differential shrinks over the years, which might appear to support the catch-up argument. But something else is going on--two things, in fact.
First, the average grades on upper-level courses generally tend to be higher than those in the early years, as students settle into their majors, which presumably are subjects they enjoy and do well in. But more importantly, black students were much likelier than white students to switch from majors in STEM and economics to other fields. Courses in STEM and economics, the authors note, "are rated more difficult" and "have harsher grade distributions than...the humanities and social sciences." In other words, students with lesser initial credentials, regardless of race, shift to less difficult fields where they are likely to receive higher grades. This, of course, "works to dissuade individuals with relatively worse academic backgrounds from persisting" in STEM majors. Because the black students started out at the lower end of the class as a result of admissions preferences, they were especially affected by this trend.
"Over 54% of black men who express an initial interest in majoring in the natural sciences, engineering or economics switch to the humanities or social sciences compared to less than 8% of white men," the study authors write. As for women, "33% of white women switch out of the natural sciences, engineering and economics with 51% of black women switching." Students with "relatively weaker academic backgrounds [are] much less likely to persist in natural sciences, engineering and economics majors." This means that "the convergence of black/white grades is then a symptom of the lack of representation among blacks in the natural sciences, engineering and economics," the authors argue. The grade point averages of black students rise over their college careers, in other words, because a higher percentage of them move to less difficult and higher-graded majors.
So a major effect of racial preferences at this elite college appears to be encouraging many minority students to major in fields other than STEM. That is because "affirmative action," the authors observe, "primarily affects where minorities enroll in college, not whether they enroll, pushing students up through the school quality distribution." Without preferences, these students would very likely attend somewhat less elite colleges, where their credentials would likely place them in the middle or top of the admitted class. They would thus have "a higher probability of persisting in a science major." Because the difficulty of STEM classes drives away every school's "least prepared students" who, because of admissions preferences, are often members of racial minorities, "affirmative action may be working to increase the number of non-science majors [among minority students] at top schools at the expense of science majors at less-selective schools."
The nation has spent "much money on encouraging minorities to enter the sciences"--to be exact, more than $1.5 billion from the National Science Foundation and $675 million from the National Institutes of Health. Admissions preferences, however, appear to be "working against these goals."