Looking at Prediction from an Economics Perspective: A Response to Harcourt's Against Prediction.

This article discusses Bernard E. Harcourt's Against Prediction: Profiling, Policing, and Punishing in an Actuarial Age (2007 ). The book opposes the use of probabilistic methods, such as profiling, on efficiency, equity, and jurisprudence grounds. By contrast I argue that profiling is always efficient, that there is no theoretical flaw in reliance on actuarial methods, as long as they are implemented properly. I also show that the equity-based criticism of reliance on actuarial methods (Harcourt's ratchet effect argument) is based on two questionable assumptions: that profiling is perfectly efficient (as zero deterrence is assumed), and that the police are making an obvious logical mistake, by gradually increasing the extent to which they target the group with the higher offending rate instead of targeting only them in the first place.