Recidivism is the return to a behavior. The term is commonly used specifically to refer to the return to criminal behavior (see, for example, Maltz 1984). When criminals reoffend, they are called recidivists. Those who continually recidivate, or persist at crime, are sometimes called persisters, whereas those who cease, or desist from, criminal activity are referred to as desisters (see Blumstein, Farrington, and Moitra 1985). Recidivism is important to policy makers and those responsible for public safety because studies suggest that persisters, particularly high-rate persisters, arre responsible for a disproportionate amount of crime (Chaiken and Chaiken 1982; Wolfgang, Figlio, and Sellin 1972). Some researchers have suggested that if persisters could be accurately identified before they reoffend and restrained through imprisonment, society could realize considerable reductions in crime at reasonable costs (Greenwood 1982). Others, however, point to practical difficulties in identifying such individuals and ethical concerns with punishing individuals for what they are expected to do in the future. (See Blumstein et all. 1986:128-43 for a summary of the issues.) The concept of recidivism appears to be a simple one. Someone who has committed one crime commits another. However, upon further consideration, recidivism - like crime - encompasses a variety of dimensions. Three common dimensions are crime type (violent versus property crime, for example), seriousness (siimple assault versus murder), and frequency (daily versus annually). An additional complication to the consideratin of recidivism is that it is difficult to measure because crimes are seldom observed. Thus prozies such as arrest of incarceration often are used as measures of recidivism. Finally, although a number of characteristics of offenders have been identified that are associated with recidivism, models or tools to predict recidivism, models or tools to predict recidivism still are inadequate to identify accurately only those who would - if free - commit new crimes.