Seizures data — an overview of the methods and definitions used
Data on drug seizures relate to all seizures made in each country during the year by all law enforcement agencies (police, customs, national guard, etc.). Caution is required in relation to double-counting that might occur within a country — although it is usually avoided — between various law enforcement agencies.
Seized quantities of cannabis, heroin, cocaine and amphetamine are provided in kilograms, of LSD in doses, and of ecstasy in tablets. Quantities seized may fluctuate from one year to another, due to a small number of large seizures. For this reason, the numbers of seizures are usually considered as a better indicator of trends. In all countries, they include a major proportion of small seizures from the retail level of the market. All trend data, though, are subject to extraneous influences affecting them, e.g. changes in legislation, changes in police practices, etc.
For more information see: Information map on law enforcement sources