The implications of jail time discounting for court sentences

Specific and marginal general deterrence are being increasingly discredited as useful sentencing objectives. One reason is that offenders discount jail time, sometimes quite substantially. As a consequence, there is a significant difference between the court's sentence and the effective penalty. The latter is the offender's perceived duration of the time in jail. Discount rates, which perhaps can be thought of as a measure of acclimatisation to the prison experience, potentially weaken considerably the likelihood of successfully attaining the objective of specific deterrence. In addition, since jail time discount rates increase as the sentence length increases, punishment burden increases less than proportionately. This means that successfully achieving marginal deterrence is even more problematical. Using New South Wales data for three different offences, mean estimates of jail time discount rates are obtained, and then used to adjust downwards court sentences and estimate their effective equivalents. Effective sentence elasticities are then computed to gauge the impact of sentence doubling. Very low values are obtained. The critical implications for sentencing suggested by this study are, first, that absolute general deterrence and specific deterrence are realistic sentencing objectives. Marginal deterrence, however, does not seem to be attainable, given the ubiquity of positive time preference. Secondly, subject to the proportionality constraint, relatively shorter sentences are likely to be more punitive than longer ones, and therefore more effective as specific deterrents.