[Excerpt] In many respects the structures of the workers' compensation and unemployment insurance systems are similar. Each is actually a system of individual state systems. Both are financed by a payroll tax that is imperfectly experience rated. Both provide insurance against an adverse consequence (work injury or unemployment) that leads to time away from work; the incidence and duration of these events are at least partially determined by both employer and employee behavior. Both systems provide, at least for temporary events, a structure of benefits that ties compensation to a worker's previous earnings. Because of these similarities, it is not inappropriate for an individual such as myself, who has conducted some research on the unemployment insurance system but none on the workers' compensation system, to provide an analysis and summary of the effects of the latter on work injury experience. Indeed, one contribution of this chapter will be to point out how lessons learned from research on other forms of social insurance can be applied to research on workers' compensation. Nonetheless, there are important differences in, and complexities of, the workers' compensation system that analyses of it must take into account; these are highlighted as well.