This Article reviews the empirical research on the effectiveness of monitoring and enforcement of environmental policy in deterring individuals and firms from violating environmental laws or achieving an improved level of environmental performance. It considers both "monitoring" activities (such as government inspections) and "enforcement" activities (such as sanctions, remedial actions, and other mechanisms designed to punish and/or bring a firm into compliance). It also evaluates "informal" monitoring and enforcement pressures, such as the role that public information has on firm compliance. However, it does not consider the role of liability laws (torts, nuisance actions, etc.) in compelling polluters to reduce emissions.¹ Likewise, except for a few studies in Canada, it does not address enforcement analyses conducted outside the United States.²

Until recently, there have been surprisingly few empirical studies of environmental enforcement. Comprehensive data on compliance and enforcement are only beginning to become available to researchers. Thus, the few studies that have been published focused either on oil spills (where the U.S. Coast Guard maintains a comprehensive data set), or on specific industries such as the pulp and paper industry, where the U.S. Environmental Protection Agency (EPA) funded and/or assisted researchers in their data collection efforts. Data availability is rapidly changing as EPA has integrated all of its enforcement and monitoring data by facility and is beginning to make facility-level data freely available to the public on their website. Thus, this is an opportune time to take a fresh look at the theory and evidence of environmental deterrence.