There seem to be two prevailing conceptions of class actions.  In one view, a class action is a way of determining many similar claims at once by evaluating common evidence that reliably establishes liability (and lays a ground work for efficiently calculating damages) for each class member.  That is, the class device produces the same results as individual actions would, but more efficiently.  In the other view—one we consider misguided—a “class” of plaintiffs complaining about similar conduct can have their claims determined through statistical sampling even if no common evidence will provide a common answer to common factual or legal questions. Instead, this theory holds, the results of mini-trials can simply be extrapolated to the entire class, even if individual results would vary widely.

Last week, the Ninth Circuit took a step deeper into the second camp in Jimenez v. Allstate Insurance Co. (pdf), delivering a ringing endorsement of statistical sampling as a way to establish liability as well as damages.