Measuring the Long-Term Effects of Public Policy: The Case of Narcotics Use and Property Crime

The effects of treatment and legal supervision on narcotics use and criminal activities were assessed by applying newly developed time-series methods that disentangle the long-term (permanent) and the short-term (temporary) effects of intervention. A multivariate systems approach was used to characterize the dynamic interplay of several related behaviors at a group level over a long period of time. Five variables---abstinence from narcotics use, daily narcotics use (or addiction), property crime, methadone maintenance treatment, and legal supervision---were derived by aggregating information from over 600 narcotic addiction histories averaging 12 years in length. Because of the long assessment period, age was also included as a control variable. Overall, the system dynamics among the variables were characterized by long-term rather than short-term relationships. Neither methadone maintenance nor legal supervision had short-term effects on narcotics use or property crime. Methadone maintenance treatment demonstrated long-term benefits by reducing narcotics use and criminal activities. Legal supervision, on the other hand, did not reduce either narcotics use or property crime in the long run. Instead, there was a positive long-term relationship in which a higher level of legal supervision was related to higher levels of narcotics use and criminal activity. This latter finding is consistent with the observation that either narcotics use or criminal activity is likely to bring addicts to the attention of the legal system. However, these addicts, as a group, did not directly respond to legal supervision by changing their narcotics use or crime involvement except perhaps through coerced treatment. The paper explores the policy implications of these findings.