Ct. at 1432, and "affirmatively demonstrate [their] compliance with the Rule," Wal-Mart, 131 S. Ct. at 2551. "[S]ome evidence" is not enough. In re Initial Pub. Offerings ["IPO") Sec. Litig., 471 F.3d 24, 33 (2d Cir. 2006). Before certifying a class action, courts will require a plaintiff to establish by a