Overall recidivism rates (48-month follow-up)

Across the entire sample of offenders released from New Zealand prisons in 2002/03, 49 percent were convicted of a new offence and were returned to prison at least once during the 48-months follow-up period.

Graph 1: Reimprisonment rate by time to first re-offence

To clarify the above graph, the shape of the two curves is illustrative of the relationship between the volume of offenders re-imprisoned and elapsed time over the four-year follow-up period. The lower (blue) line is the cumulative proportion re-imprisoned, and indicates that numbers rise steadily early in the follow-up phase, such that by the one-year mark, 26 percent of the sample had already been reconvicted and returned to prison. By the two-year mark 37 percent had been returned to prison, by the three-year mark 44 percent of the sample, with the 49 percent figure attained by 48 months.

The upper (red) curve in the above graph shows the proportion of all re-imprisoned (in percentages) who had been returned to prison by successive three-monthly intervals. This shows, for example, that of those who were reconvicted, just over half (54 percent) were re-imprisoned within the first twelve months. From that point the rate of “relapse” slows, with a further quarter (22) percent returned to prison by the 24-month point, 14 percent returned to prison by 36 months, and the remaining ten percent returned to prison over the final twelve months. The shape of this curve predicts that, in a further twelve months time (after five years follow-up), around 52 percent of the entire sample will have been returned to prison at least once. Thereafter, new imprisonments from amongst those in the original cohort, who had not been re-imprisoned by that time, can be expected to be very small in number.