Frederick Hess and Grant Addison point out an anomaly:
In Griggs v. Duke Power Company (1971), the Supreme Court unanimously interpreted this language to mean that when a selection process disproportionately affects minority groups (e.g. has a “disparate impact”), employers must show that any requirements are directly job related and an accurate predictor of job performance. . . .
[I]f companies require job applicants to possess an IQ of 110, they must be able to demonstrate why an applicant with an IQ of 109 is incapable of performing a job that someone with a 110 IQ can. One need only read that sentence to understand why human-resource lawyers quiver in horror when executives ask about using that kind of screening test. . . .
College-degree requirements, meanwhile, have escaped scrutiny.
Bryan Caplan notes, however, that there is a big loophole in the restrictions on employers’ use of IQ testing: “Employers can’t safely request standardized test scores, but to the best of my knowledge, applicants can safely provide them.” The fact that applicants rarely volunteer this information, and that employers do not reward them for doing so, suggests to Caplan that the practical effect of the restrictions is not large.