One reason disparate impact theory has become such a standard element in institutional affairs is that it is so simple.  It begins and ends on a basic numerical axiom: if a practice affects an identity group disproportionately, we have some kind of bias at work.  It offers as evidence only a ratio, for instance, a much lower percentage of African American students majoring in STEM fields that the percentage of African Americans in the general population. One doesn't have to prove a racist intent on the part of an organization or individuals within it, nor does one have to identify a specific act of discrimination.  The bare existence of disproportion signifies a problem.

In actual legal proceedings, things get more complicated, but the press has adopted disparate impact as a handy story line.  We see its influence in this story in the Chronicle of Higher Education on a contested tenure case at University of Southern California. Note the headline: "Tenure Decisions at Southern Cal Strongly Favor White Men, Data in a Rejected Candidate's Complaint Suggest."  Decisions "favor" white men?  That's a tendentious description of a statistical disparity, specifically, that white men in the social sciences and humanities are tenured at USC at a 92 percent rate, while female and minority professors earn tenure at only a 55 percent rate.  The verb "favor" puts the action entirely in the hands of the people making the tenure decision, leaving the candidate for tenure not an individual with a strong or weak record, but merely a representative of an identity group.

The rest of the article sticks with that angle.  The case involves a political science professor, a woman with a Hawaiian and Asian background, who was denied tenure and has filed a Federal lawsuit, her primary grounds (according to the story) being procedural errors and disparate impact.  She and a colleague compiled a history of tenure cases and found the vast discrepancy, leading her to state in a news release that she aims ""to correct the unfair damage to my career and to help assure that women and minority candidates will have the same chance to earn tenure as do their white, male colleagues."

USC has no comment on the affair, and we don't know the specifics of why the denial happened.  A blog post by a USC professor noted that the Office of Equity and Diversity investigated her charges and found no evidence of bias, but the disparate impact numbers still stand firm.  That's the beauty of disparate impact theory.  The facts in individual cases don't matter.  It's the "pattern" that stands out, and it licenses advocates to call for remedies no matter how much the institution demonstrates good faith.  In USC's case, the idea that affirmative action in hiring might have produced a difference in accomplishments between a disfavored group (white males) and all other groups doesn't even arise as a possibility.