Brattle assisted Polaris – a US manufacturer of motorcycles, snowmobiles, and all-terrain vehicles (ATVs) – in obtaining a victory at the class certification stage of a closely watched product liability case. The plaintiffs alleged that Polaris had failed to disclose information on alleged exhaust heat issues in thousands of its ATVs, causing consumers to overpay for these ATV models. The plaintiffs’ experts claimed to have considered both supply and demand when establishing the amount of the alleged overpayment. However, Brattle’s expert testimony explained that both the survey-based demand analysis and the equilibrium model that the plaintiff used to determine the amount of the alleged overcharge were unreliable. The district court judge denied certification of the class, ruling that the plaintiffs’ expert-driven overcharge theory was insufficient to meet class certification requirements. On appeal, the Eighth Circuit affirmed the district court’s ruling.