In Jones v. City of Boston, the District Court granted the City's motion for summary judgment and rejected police officers' disparate impact race discrimination claim based on the Equal Employment Opportunity Commission's (EEOC) "Four-Fifths Rule."

The Boston Police Department uses hair testing to determine if its officers are using illegal drugs. The plaintiff officers failed the hair test and suffered adverse employment actions. The officers sued the City , claiming that the hair test had a disparate impact on African-Americans and thus violated Title VII and Chapter 151B.

The plaintiffs relied on expert statistical evidence in their attempt to establish a prima facie case of disparate impact discrimination. The plaintiffs' expert found evidence that differences in the rates at which African-Americans failed, rather than passed their hair test, were statistically significant. Although it was undisputed that during an eight-year period African-American officers had passed the test at rates between 97% and 99% and white officers passed at rates between 99% and 100%, the plaintiffs argued that their evidence revealed a statistically significant disparity that satisfied their prima facie burden. The District Court disagreed.

The District Court stated that to establish their prima facie case the plaintiffs must identify statistical disparities that are sufficiently substantial that they raise an inference that an employment practice disparately impacts an identified racial group. No one test controls in measuring disparate impact. The District Court observed that the First Circuit has approved the EEOC's "Four-Fifths Rule," which is a rule of thumb for measuring the sufficiency of statistical evidence in employment cases. This rule states that a selection rate for one race that is less than four-fifths of the selection rate of the group with the highest rate will be regarded as evidence of disparate impact. Conversely, a greater than four-fifths rate will generally not be regarded as evidence of disparate impact.

Applying the Four-Fifths Rule here, the District Court held that the plaintiffs failed to establish a prima facie case and "the question is not even close" because "the passing rate for African Americans was at least 97% of the passing rate for whites." The District Court rejected the plaintiffs' reliance on the statistical significance of failure rates, stating that "[f]ocusing on failure rates, rather than passing rates, eludes the point of the Four-Fifths Rule, where the EEOC addressed 'selection' rates rather than 'exclusion' rates."

Employers should consider utilizing the Four-Fifths Rule when assessing whether any practices, including hiring and promoting examinations, have an unintentional disparate impact on a protected group.