Affirmative Action's Affirmative Actions: A Reply to Sander

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I am grateful to Professor Sander for his interest in my work and his willingness to pursue a valid answer to the critical question of the effects of law school tier on bar performance. Sander's readiness to respond to my Comment (1) demonstrates the importance of the questions at hand and his openness to progress on these issues. Fortunately, progress is possible, because, as I show here, the impressive-sounding points in Sander's Response (2) violate basic methodological principles and are incorrect.

Sander points to certain descriptive facts that my Comment does not dispute. Black students appear to fail the bar at higher rates than white students. It also appears that "blacks and whites with similar law school grades (when controlling for school and entering credentials) have virtually identical graduation and bar outcomes." (3) However, these descriptive observations are irrelevant to the causal question of whether going to a higher-tier law school causes black students to fail the bar. As my Comment and this Reply demonstrate, black law students who are similarly qualified when applying to law school perform equally well on the bar irrespective of what tier school they attend. There is no evidence that affirmative action reduces the bar performance of the students it is designed to help. The descriptive facts Sander presents may account for some of the reasons for affirmative action, but they do not address the consequences of affirmative action. Here, I respond to each of Sander's points in turn.

First, Sander's control group, as he conceives it, is invalid. As I noted in my Comment, every law school examined practices some form of affirmative action, so the data is not informative about the broad effects of affirmative action. Instead, we may investigate the effects of attending a higher-tier law school. In response, Sander asserts that white students are the control group and black students are the treatment group, because only blacks were admitted under a system of affirmative action. (4) This conception is incorrect, because black students could differ from white students in all sorts of respects that are not due to affirmative action or law school tier. This flaw is akin to assigning estrogen to a group of women and a placebo to a group of men, and inferring the effect of estrogen on health outcomes by comparing women and men. The black/white test score gap has been documented across a host of fields, so other differences (like primary school education, family structure, or culture) may be at work. (5) Comparing blacks and whites in order to infer the causal effect of law school tier ignores all of these other differences between these groups and thereby provides an invalid estimate of the causal effect. (6)

Second, Sander asserts that controlling for law school grades does not bias the estimate of the causal effect of law school tier. He does not take issue with the rule of inference that controlling for a consequence of the cause is never justified and will never produce the right causal effect. (7) This rule is undisputedly violated here, because Sander's analysis itself demonstrates that going to a higher-tier law school decreases law school grades (8) and that law school grades are correlated with bar passage. (9) Sander's responses to this basic flaw do not withstand scrutiny. Standardizing grades within schools is no solution, because the same student may receive lower grades in a higher-tier school even if she learned the same amount. Moreover, the fact that law school GPA is the variable with the biggest effect in Sander's regressions (10) is not surprising at all. In fact, it is an indicator of the problem: This coefficient reflects the fact that his regression is controlling away the consequences of law school tier, the key causal variable. As my Comment demonstrates, omitting law school grades from the original regressions leads the coefficient on law school tier to be indistinguishable from zero and the coefficient on black students to be substantially negative. …