Of all people with some form of Corrections history post-1960 that are still under the age of 65 (390,581 people), 28% (or 108,462 people) were receiving a main benefit at 30 June 2013. This compares with approximately 11% of the NZ working-age population as a whole.Actually, I find this level of benefit dependency surprisingly low.
What it does show is people with criminal convictions have a good chance of becoming self-sustaining. I expect though that if the data was further analysed, those who serve prison-time (as opposed to community sentences) would have a higher incidence of benefit receipt.
It looks like MSD will do further work in this area, so my expectation will be confirmed in time.