Competing risks, persistence and desistance in analyzing recidivism.

A statistical procedure is developed to analyze recidivism in samples which are subject to the presence of desisters and to multiple modes of reconviction. This allows for a more accurate study of individuals' transition and hazard in the type and timing of offenses following a specific type of conviction. The use of a nonparametric approach for investigating failure in the presence of other acting causes is shown ; initial estimators of the probabilities of reconviction for different types of offenses are obtained, and the method can be used both to display the data and to choose an appropriate parametric family for the survival times. An exponential mixture model for competing risks is presented in such a way that it allows us to adjust for concomitant variables and to assess their effects on the probabilities both of reconviction for predetermined types of offenses and desistance and of the hazards of reconviction; a method for assessing calibration of predicted survival probabilities is suggested. A 21-year follow-up of persons convicted of indecent assault on a female in 1973 illustrates the methods; we find a high probability of sexual reconviction for individuals with previous sexual convictions and evidence of diversity and a raised hazard of reconviction for young chronic offenders.