A group of current and former shareholders (plaintiffs) of Occidental Petroleum Corp. (Occidental) (defendant) sued Occidental. The shareholders argued that Occidental had defrauded them in violation of SEC Rule 10b-5, and they sought certification as a class. The shareholders alleged that Occidental’s directors had made false statements and provided misleading information, causing Occidental’s stock to be artificially inflated. The proposed class members had all purchased stock during a five-year span when the alleged misinformation had been spread. The trial court certified the class. The defendants appealed, arguing that class certification was an abuse of discretion.