A provider's performance report consists of his service average outcome and volume. The two variables depend on the provider's private quality type and current demand, but he can raise his average outcome by dumping vulnerable consumers. Prospective consumers infer providers' qualities from their reports. Performance reporting drives some providers to dump consumers when competition is intense, but it may not reveal providers' qualities when their average quality is high. Statistical adjustment aiming at making reports independent of consumer characteristics can lead to more dumping, less informative reports, or both. There is more dumping when volume information is withheld and less dumping when ratings information is coarse.