The first market size estimates for cannabis, cocaine, MDMA, amphetamines and heroin were published in the EMCDDA‐Europol 2016 European Drug Markets Report, covering 2013. The challenges in obtaining such estimates were recognised at that time, though the need to assist policymakers in prioritising interventions by providing information on the scale, relative importance and changes in the markets for different drugs outweighed these concerns. The project was seen as a process, where the estimates would be improved in subsequent rounds by addressing data issues and developing the methodology. Since 2016 additional and different data sources have become available and where appropriate the methodology has been changed, though the basic underlying method remains as it was.

Developments for the estimates published in this report include:

  • data on the amounts of drugs used by various types of user have been extended and updated, using information from the European Web Survey on Drugs (EWSD);
  • routinely monitored data from the Member States have been updated, improving estimates of the number of users and drug prices. For example, 24 of the EU countries have reported a more recent general population survey than that available when the initial estimates were made;
  • crack use by high‐risk opioid users has been included in the cocaine market size estimates;
  • data on patterns of use for cannabis herb and resin, separately obtained from the EWSD, have been used to estimate the contribution of these different forms of cannabis to the overall cannabis market. In the previous estimates, numbers of seizures were used in the absence of suitable information about use of these products.

The hidden nature of the topic, the limitations inherent in some of the available data and the need for simplifying assumptions contribute to uncertainty around the estimates. Alternative methods of estimation were considered and are mentioned in the report, though each has its own data issues and weaknesses. The demand‐side approach remains the favoured method, though it is recognised that the estimates are the outcome of the approach adopted, and alternative approaches will generate different values.

Some key principles underpinning the approach taken are:

  • wherever possible, the data used came from routine data collections held by the EMCDDA to facilitate the planned process of improving and updating over time;
  • European estimates were obtained by summing individual country estimates;
  • where imputation of missing data was necessary, as far as possible, this was based on other related data;
  • every effort has been made to note all imputations and assumptions made within the estimation process, so that the limitations are clear.

As with the initial estimates, the 2017 figures are likely to underestimate the market; given the available data from which they were constructed, and despite their substantial size, these estimates should be considered as minimum values. Country estimates have not been produced, given issues of comparability in the data, the focus remaining on obtaining EU estimates of the quantity and value of the market for cannabis, cocaine, MDMA, amphetamines and opioids. A consequence of this process is that the 2013 and 2017 estimates are not directly comparable and should not be interpreted as a trend.