Measuring the impact of drug law enforcement (DLE) practice on illicit drug markets is a
notoriously difficult task. Conventional approaches to assessing DLE performance focus on
the use of drug seizure and arrest data. However, these data say more about the extent to
which police engage in certain types of activities and allocate resources than they do about
DLE effectiveness because offences relating to illicit drugs are far more likely to be detected
by law enforcement agencies than reported to them. As such, the more effort and resources
DLE invest in detecting illicit drugs, the more likely it is that drugs will be seized. On the
one hand, DLE can potentially claim success for not seizing any drugs—that is, based
on the absence of seizures and arrests, it could be argued that there is no drug problem.
Conversely, a lack of seizures and arrests could lay police open to substantial criticism for
failing to address the drug problem.