Using supply indicators in the evaluation of drug supply reduction - Challenges and opportunities

Interventions to tackle the supply of drugs, are seen as standard components of illicit drug policies and drug market-related administrative data, such as seizures, price, purity and drug-related offending, are widely used for policy monitoring and evaluation. However, these data are not primarily collected for this purpose, which makes interpretation and analysis difficult. Examples of limitations of these data sources include: the extent to which they reflect operational priorities rather than impact on drug supply; question marks over the robustness of and consistency in data collection methods; and issues around the timeliness of data availability.
Making sense of such data is therefore challenging and extreme care needs to be taken when using it. Nevertheless, given the considerable resources invested in drug supply reduction, understanding the impact of these interventions is essential, so improving the quality of the data collected and expanding its scope should be a priority for those seeking to understand or monitor drug markets and supply reduction. In addition to highlighting some of the potential pitfalls in using supply indicators for policy evaluation, this chapter presents some options for improvements based on the current European Monitoring Centre for Drugs and Drug Addiction programme of work to develop their supply-related monitoring and analysis. The conceptual framework developed to underpin this work may have wider applications and has the potential to provide a richer picture of drug markets, at both national and international levels, to aid efforts to evaluate drug supply reduction policies.