Across these studies, the authors identify five types of evaluation questions and indicators, three types of data sets, and two study designs that have been used. Evaluations may highlight the intended and unintended effects of a legal change, but there can also be unexpected effects, and the full picture will describe not only the unintended but also the unexpected effects. Evaluations should not be taken as black and white proof that one law is better than another; an objective and authoritative study result will be obtained by good design, questions and indicators that reflect a wide variety of concerns, and appropriate data sets. Such studies can be solid grounds on which policymakers can base their decisions on future changes.
European Monitoring Centre for Drugs and Drug Addiction (EMCDDA)
April, 2010