Drug seizures in a country are usually considered an indirect indicator of the supply and availability of drugs, although they also reflect law enforcement resources, priorities and strategies, as well as the vulnerability of traffickers to national and international supply reduction activities, and reporting practices. Quantities seized may fluctuate widely from one year to the next, for example if in one year a few of the seizures are very large. For this reason, the number of seizures is sometimes a better indicator of trends. In all countries, the number of seizures includes a major proportion of small seizures at the retail (street) level. Where known, origin and destination of drugs seized may indicate trafficking routes and producing areas. The price and purity/potency of drugs at retail level are reported by most of the Member States. However, data come from a range of different sources, which are not always comparable, making accurate comparisons between countries difficult.