Economic experts can assist in demonstrating that Rule 23’s prerequisites have or have not been satisfied. An expert may present economic evidence on the presence or lack of conflict within the putative class, whether class-wide impact is demonstrable through common proof, and the existence or nonexistence of a feasible and formulaic approach to measuring damages. The expert typically focuses on several key considerations, including the following:
• whether all class members have suffered injury due to the challenged conduct;
• whether the plaintiff can prove the elements of a claim (e.g., market definition, market power, and anticompetitive effects in antitrust cases) with evidence common to class members;
• whether aggregate damages can be estimated with a common formulaic method based on standard and well-accepted economic techniques; and
• whether common evidence exists sufficient to do these analyses, including proof of injury and damages, or whether specific evidence is needed for each class member.
Courts increasingly are requiring that the plaintiff provide detailed economic evidence in support of the class-certification motion See, e.g., “The Law and Economics of Class Actions: Yesterday, Today, and Tomorrow,” in 26 Research in Law and Economics (James A. Langenfeld ed., 2014). For example, in antitrust cases, courts are requiring such evidence to show that common impact can be proven at trial with evidence and analytical methods that are common to members of the class, rather than through individualized proof. Courts are requiring not only a description of the economic theory and econometric methodology that may be used to demonstrate common impact at trial but also that the economic expert actually apply these methods to the evidence to show that such common proof is feasible.