A theoretical model of deterrence is studied in which the imposition of nonmonetary (as opposed to monetary) sanctions is socially costly. It is therefore desirable that the system of sanctions be designed so that sanctions are imposed infrequently. If courts possess perfect information, the optimal system is such that sanctions are never imposed--all who can be deterred will be--but, realistically, courts' information will be imperfect and sanctions will be imposed.

Optimal enforcement of law is examined in a model with specific enforcement effort--effort devoted toward apprehending individuals who have committed a single type of harmful act--and general enforcement effort--effort devoted toward apprehending individuals who have committed any of a range of harmful acts (a police officer on patrol, for instance, is able to apprehend many types of violators of law). If enforcement effort is specific, optimal sanctions are extreme for all acts. If enforcement effort is general, however, optimal sanctions rise with the harmfulness of acts and reach the extreme only for the most harmful acts.

Self-reporting--the reporting by parties of their own behavior to an enforcement authority--is a commonly observed aspect of law enforcement, such as in the context of environmental and safety regulation. We add self-reporting to the model of the control of harmful externalities through probabilistic law enforcement, and we characterize the optimal scheme. Self-reporting offers two advantages over schemes without self-reporting: enforcement resources are saved because individuals who report their harmful acts need not be detected, and risk is reduced because individuals who report their behavior bear certain rather than uncertain sanctions.

The primary purpose of unemployment insurance (U.I.) is no doubt to insure individuals against loss of wage income. However, U.I. is commonly believed to adversely affect job search behavior and to lengthen the duration of unemployment. With these issues in mind, this paper asks how U.I. benefits ought to be paid out over time. Specifically, the paper uses a theoretical model to determine characteristics of the time sequence of benefits that maximizes the expected utility of the unemployed, given that they act in a self-interested way and given the total size of the U.I. budget.