The size of a market is based on factors influencing both demand and supply. Changes in market size, therefore, provide valuable information about the net effects of movements in both parts of the market. For example, while the number of users may decrease in response to a prevention policy targeting initiation, total expenditures may simultaneously increase due to factors shifting more light users into heavy use or an increase in supply. Therefore, estimating the size of the market, in terms of both participants and expenditures, is critical to fully understanding the impact of interventions intended to influence demand and/or supply. This report uses data on the prevalence of drug use, retail prices, and consumption patterns to generate country-level consumption and retail expenditure estimates for cannabis, heroin, cocaine, and amphetamine-type substances. Major findings include: global retail expenditures on cannabis to range from 40B-120B Euros, and our best estimate is close to half of the previous global estimate of approximately 125B Euros; exporting cocaine hydrochloride from Colombia to consuming countries generates a value of no more than 10B Euros annually (import price-replacement cost), and the equivalent value for opiates exported from Asia and the Americas is no more than 20B Euros; surprisingly little is known about typical quantities consumed of illicit drugs, which makes generating demand-side estimates difficult. For cannabis, much could be learned by adding a few questions to existing surveys. For harder drugs, arrestee surveys can provide a wealth of information.

"Prepared for the European Commission"--T.p. "This study has been produced by the Trimbos Institute and RAND with the financial support of the Commission of the European Communities"--T.p.

Introduction -- Methodological issues associated with demand-side estimates -- Cannabis -- Heroin -- Cocaine -- Amphetamine-type substances -- Conclusions -- Appendix A: farm-gate and international trade values for cocaine and opiates -- Appendix B: GDP estimates for 2005 -- Appendix C: information about other major opiate markets.