"Overall, supply reduction—that is, reducing the availability of drugs—does not appear to have played as major a role as many had assumed in four of the five most important downturns in illicit drug use that have occurred to date, namely, those for marijuana, cocaine, crack, and ecstasy (see, for example, Figures 8-4, 8-5, and 8-6). The case of cocaine is particularly striking, as perceived availability actually rose during much of the period of downturn in use that began in the mid- 1980s.