Although it will take more time to fully digest the Court's Wal-Mart v. Dukes decision, released earlier today, the majority's reaction to the statistical evidence brought by the respondents (plaintiffs) is clear. Central to the respondents’ case were results from regression analyses that aggregated data from individual Wal-Mart stores. The Court did not find the aggregated results sufficient to support the necessary inference of uniform, store-by-store discrimination upon which the respondent's legal theory of commonality (for class certification purposes) relies. An excerpt from the Court's opinion follows.
"The statistical evidence consists primarily of regression analyses performed by Dr. Richard Drogin, a statistician, and Dr. Marc Bendick, a labor economist. Drogin conducted his analysis region-by-region, comparing the number of women promoted into management positions with the percentage of women in the available pool of hourly workers. After considering regional and national data, Drogin concluded that “there are statistically significant disparities between men and women at Wal-Mart . . . [and] these disparities . . . can be explained only by gender discrimination.” 603 F. 3d, at 604 (internal quotation marks omitted). Bendick compared work-force data from Wal-Mart and competitive retailers and concluded that Wal-Mart “promotes a lower percentage of women than its competitors.” Ibid.
Even if they are taken at face value, these studies are insufficient to establish that respondents’ theory can be proved on a classwide basis. In Falcon, we held that one named plaintiff’s experience of discrimination was insufficient to infer that “discriminatory treatment is typical of[the employer’s employment] practices.” 457 U. S., at 158. A similar failure of inference arises here. As Judge Ikutaobserved in her dissent, “[i]nformation about disparities at the regional and national level does not establish the existence of disparities at individual stores, let alone raise the inference that a company-wide policy of discrimination is implemented by discretionary decisions at the store and district level.” 603 F. 3d, at 637. A regional pay disparity, for example, may be attributable to only a small set of Wal-Mart stores, and cannot by itself establish the uniform, store-by-store disparity upon which the plaintiffs’ theory of commonality depends."