Models pertaining to how drug policy should vary over the course of a drug epidemic.

The goals of this chapter are three-fold: (1) to outline some broad empirical regularities concerning how drug problems evolve over time, (2) to sketch some plausible mechanisms for ways in which aspects of that variation might be endogenous, and (3) to review two classes of dynamic models of drug use that have implications for how policy should vary over a drug epidemic.