At European level, research into public expenditure is gaining momentum, in view of the growing realisation that policy evaluation with regard to drugs is important. After all, public expenditure is an important indicator of governmental efforts to tackle the drug problem. With this study we want to untangle the existing confusion with regard to public expenditure studies. Public expenditure studies are reviewed in terms of the concepts and methodologies used. Public expenditure and social cost models are compared to determine the scope of both concepts. A proposed definition of public expenditure is presented and a workable methodology is elaborated for estimating public expenditure
that can be applied to other criminological policy domains, and as such might stimulate the development of evidence-based policies. Studies dealing with the estimation of public expenditure were searched by consulting search engines, scientific on-line databases and websites in the field of drugs. It becomes clear that there is no common understanding of the meaning of “public expenditure” and “social cost”. Very different concepts are used interchangeably or the same terminology is used, yet with definitions and interpretations that can differ widely. Studies also differ concerning the classification and measurement of public expenditure. The methodology necessary to study public expenditure on drugs is complex because different policy areas (prevention, treatment and law enforcement) and different governmental levels (local, regional and federal) are involved. Ideally, two methods of analysis are combined: a top-down approach, analysing the funding sources of the private and public organisations and a bottom-up approach, analysing the activities in the work field. For the calculation of public expenditure, a distinction has to be made between explicitly labelled drug-related
expenditure and non-labelled drug-related expenditure. The methodology applied to study public expenditure on drugs can be used to study governmental investments and priorities in other policy domains, where typically an integrated approach is strived for. The results of public expenditure
studies can be used to modify or rationalize public expenditure. Research into public expenditure is important for each policy domain to meet the requirements of an evidence-based policy and is the first step to effectiveness research.