Chapter 7 Empirical Study of Criminal Punishment This chapter reviews empirical studies of criminal punishment and the criminal justice system by economists. Since the modern exposition of the economic model of criminal behavior empirical economists have tested its predictions using variation in expected criminal punishments. In the past decade empirical economists have made substantial progress in identifying the effects of punishment on crime by finding new ways to break the simultaneity of crime rates and punishments. The new empirical evidence generally supports the deterrence model but shows that incapacitation influences crime rates too. Evidence of the crime reducing effect of the scale of policing and incarceration is consistent across different methodological approaches. Estimates of the deterrent effect of other penalties such as capital punishment are less robust and suggest that claims of large effects from these policies may be spurious. More work is needed to assess the relative importance of deterrence and incapacitation. Empirical economists have made less progress in studying the criminal justice system itself. Data availability constrains the economists ability to resolve the simultaneity of criminal justice institutions and crime rates and this limitation hampers rigorous empirical investigation of the incentive effects of numerous criminal justice institutions and procedures. This area remains an important avenue for future empirical research.