Cook's focus is on the economical use of crime control, which involves an assessment of the cost of crime-control methods in relation to their effectiveness in reducing crime costs, i.e., the economic effects of particular crimes on its victims and society. He criticizes the use of mass incarceration as a crime control method, because it typically has a higher cost than the cost of the crimes committed by most inmates. He suggests less costly crime control methods, such as community-based supervision and treatment, which is not only less costly than incarceration, but has proven to be equally or more effective than incarceration in reducing crime costs. Cook also promotes crime prevention as a cost-effective means of reducing crime costs. Crime prevention can reduce opportunities for crime by "hardening" the most popular targets for crimes or by early interventions for those at risk for the development of criminal behaviors.