To evaluate such policies, we should stop measuring their success according to such indicators as numbers of arrests, prosecutions and drug seizures, which turn out to have little impact on levels of drug use or crime. We should instead measure the outcomes in the same way that a business would measure the results of a new ad campaign. That means studying things like the number of victims of drug-related violence and intimidation, levels of corruption connected to the drug market, the amount of crime connected to drug use, and the prevalence of dependence, drug-related mortality and HIV infection.