Olean Wholesale Grocery Cooperative, Inc. v. Bumble Bee Foods LLC, 993 F.3d 774, 2021 WL 1257845 (9th Cir. 2021), where it held that the district court abused its discretion by granting class certification without determining the percentage of class members injured by the allegedly anticompetitive conduct. The Olean decision presents another case study in the hurdles presented to class certification by the predominance requirement, especially in cases where plaintiffs employ statistical or representative evidence to show class-wide injury at the class certification stage. In Olean, producers of packaged tuna appealed a ruling certifying three classes in a multidistrict antitrust case alleging a price-fixing conspiracy. The appellants challenged the district court’s finding that Rule 23’s predominance requirement had been satisfied by disputed expert statistical evidence showing class-wide impact on the classes “based on averaging assumptions and pooled transaction data.” 2021 WL 1257845, at *2.