Intervention Time Series Analysis of Crime Rates

The Commonwealth of Virginia abolished parole and reformed sentencing for all felony of-fenders committed on or after January 1, 1995. We examine the impact of this legislationon reported crime rates using different time series approaches. In particular, structuraltime series models are considered as an alternative to the Box-Jenkins ARIMA modelsthat form the standard time series approach to intervention analysis. Limited supportfor the deterrent impact of parole abolition and sentence reform is obtained using uni-variate modelling devices, even after including unemployment as an explanatory variabIe.Finally, the flexibility of structural time series models is illustrated by presenting a mul-tivariate analysis that provides some additional evidence of the deterrent impact of thenew legislation.