vices. In addition, they may move to areas of a city where police activity is relatively low, or they may time their operations to coincide with periods of minimal police activity.

It may seem to some that a policy of “the more law enforcement, the better” is the safest way to proceed in the absence of knowledge of the effectiveness of any given level of enforcement. It may seem to others that the absence of such knowledge justifies a reduction in the level of enforcement. Neither view is supported by existing evidence. Aggressive law enforcement is costly to society. Some costs are pecuniary and must be paid through taxes: the costs of personnel, equipment, and facilities for the police, courts, and prisons. There are also substantial nonpecuniary costs of aggressive law enforcement: the physical danger to police, inconvenience to and possibly violation of the civil rights of law-abiding citizens, increased violence associated with drug markets, and disruption of communities in which police operations occur. Thus, it cannot be concluded that more law enforcement is necessarily better. More is better only if the benefits of additional enforcement exceed its costs. It is conceivable that the costs of the existing level of enforcement exceed its benefits, in which case less enforcement activity would be better. Conversely, less law enforcement may reduce the pecuniary and nonpecuniary costs of law enforcement but may increase drug dealing, drug consumption, and the social costs associated with drug dealing and consumption. Less law enforcement is better only if the reductions in pecuniary and nonpecuniary costs of enforcement exceed the social costs associated with increased drug dealing and consumption. In summary, there is no reason to believe that the current level of law enforcement is socially optimal, but it is unknown whether optimality lies in the direction of increased or decreased enforcement.

The sections that follow summarize current knowledge of deterrence and adaptive behavior and replacement and incapacitation of dealers. The committee concludes that very little is known about the effectiveness of law enforcement operations against retail drug dealers. Substantial data-acquisition and other efforts will be needed to remedy this situation.

Deterrence theory is based on the notion that increases in the certainty, speed, and severity of punishment result in declines in criminal behavior. Empirical research on deterrence typically seeks to relate time-series or cross-sectional variation in crime rates to variations in the intensity of enforcement. Some of this research takes the form of impulse-response analyses of police crackdowns on drug markets and drunk