BACKGROUND: The importance of illicit drug price data and making appropriate adjustments for purity has been repeatedly highlighted for understanding illicit drug markets. The European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) has been collecting retail price data for a number of drug types alongside drug-specific purity information for over 15 years. While these data are useful for a number of monitoring and analytical purposes, they are not without their limitations and there are circumstances where additional adjustment needs to be considered. This paper reviews some conceptual issues and measurement challenges relevant to the interpretation of price data. It also highlights the issues with between-country comparisons of drug prices and introduces the concept of affordability of drugs, going beyond purity-adjustment to account for varying national economies.

METHODS: Based on a 2015 European data set of price and purity data across the heroin and cocaine retail markets, the paper demonstrates a new model for drug market comparative analysis; calculation of drug affordability is achieved by applying to purity-adjusted prices 2015 Price Level Indices (PLI, Eurostat).

RESULTS: Available data allowed retail heroin and cocaine market comparison for 27 European countries. The lowest and highest unadjusted prices per gram were observed for heroin: in Estonia, Belgium, Greece and Bulgaria (lowest) and Finland, Ireland, Sweden and Latvia (highest); for cocaine: the Netherlands, Belgium and the United Kingdom (lowest) and Turkey, Finland, Estonia and Romania (highest). The affordability per gram of heroin and cocaine when taking into account adjustment for both purity and economy demonstrates different patterns.

CONCLUSION: It is argued that purity-adjusted price alone provides an incomplete comparison of retail price across countries. The proposed new method takes account of the differing economic conditions within European countries, thus providing a more sophisticated tool for cross-national comparisons of retail drug markets in Europe. Future work will need to examine other potential uses of the drug affordability tool.

LIMITATIONS: The limitations of this measure reflect primarily the limitations of the constituent data; in addition to issues inherent in collecting accurate data on illicit markets, analysis that relies on data collected from multiple countries is susceptible to discrepancies in data collection practices from country to country.