Ascertainability has been, and will likely continue to be, an important requirement for class certification in the Third Circuit. Over the past decade, almost every circuit has, in one way or another, weighed in on the ascertainability debate. The Third Circuit led the way in defining a "heightened" ascertainability standard in the trilogy of decisions: Marcus v. BMW of North America, 687 F.3d 583 (3d Cir. 2012); Hayes v. Wal-Mart Stores, 725 F.3d 349 (3d Cir. 2013); and Carrera v. Bayer Corp., 727 F.3d 300 (3d Cir. 2013).