Although aggregate proof of damages can be appropriate in some settings, the Court considers such proof improper as presented in this case. The trial court erred when it initially allowed plaintiff to prove class-members’ out-of-pocket costs for brake repairs based on an estimate untethered to the experience of plaintiff’s class. The trial court properly ordered individualized proof of damages on plaintiff’s brake-repair claim based on the actual costs incurred by the class members. Thus, the trial court’s grant of defendant’s motions for a new trial and for partial decertification of the class were a proper exercise of its discretion.