The seizure of drugs is a salient consequence of a variety of U.S. enforcement programs, but particularly of interdiction. It provides evidence that the U.S. criminal-justice system is imposing costs on drug distribution. A large seizure offers the most vivid evidence that senior members of the drug trades are subject to serious risks.

Seizures from smugglers have often been used as a measure of the effectiveness of interdiction efforts. One argument suggests that the larger the quantity of drugs seized, the more smugglers have been hurt by interdiction. Others viewseizures as an indicator of the quantity smuggled; this view assumes that the share of imports seized is effectively a constant. Clearly these are extreme assumptions. The quantity seized is a function of at least three factors: the quantity shipped, the relative skill of the interdictors, and the care taken by smugglers. The...