Some critics of class actions claim that they do not deter misconduct. But this claim is entirely inconsistent with the “Chicago School” theory of internalization of costs: if corporations have to pay when they do something wrong, they will only do something wrong when the benefits outweigh the harm they cause. Some claim that corporations cannot avoid the alleged misconduct because they cannot predict when they might be sued in a class action, but this is belied by the resources they expend on risk assessment. Others claim that, even if cost internalization works in theory, there is no empirical evidence it works in practice. Wrong again: there are several studies showing that increased exposure to class action lawsuits changes corporate behavior.