Thursday, 12 August 2010

Marginal deterrence for the incarcerated

The most sensible critique I've heard of National's Three Strikes policy for New Zealand is that the abolition of parole gets rid of marginal deterrence for inmates.  If time off for good behaviour is gone, then there's no incentive for good behaviour.  And that can be pretty costly.  Of course, this could be fixed by "added time on for bad behaviour", but it's pretty plausible that the administrative costs of the parole regime are a lot lower than the extra time when it comes to burden of proof issues.  An alternative framework would keep the Three Strikes law as it is, but add on an extra margin to all sentences that would be abated in case of good behaviour.

@CrimeEconomist points to some decent evidence favouring ensuring that there's always a margin.

 It worked.  And so too did their enhanced parole system.


My best read of the evidence is that increased use of incarceration was responsible for the biggest part of the explainable part of the drop in crime rates in the US in the 1990s.  But there are lots and lots and lots of people in prison who don't need to be there.  The bang for the buck is in keeping locked up the habitual violent offenders and in ensuring that penalties for repeat violent offending are harsher than for first time offending.  But subjecting minor drug users and dealers to mandatory lengthy sentences is a good way of ramping up the costs of prison with no particular benefit for the folks paying to keep them in prison.


  1. This assumes policy is made on a rational basis. When it comes to policy such as this (well-publicised and likely to evoke strong emotion), it tends to be portrayed in emotive terms by proponents on either side, and is often less about what works and more about pushing one's view to the forefront. In this case, punishment is what's desired by its advocates, not better law or even outcomes (those are secondary to the goal). Evidence based policy, pfft. Not when short-term interests dominate and whoever's in power is unlikely to have to deal with the problems such poor policy creates.

  2. @Jive: Oh, I've never assumed policy is made rationally. I wish it were so, but I'd have a lot less to shout about on the blog were it the case.

  3. I guess the incentive for good behaviour doesn't need to be early parole. This could be substituted with other things inmates might value, perhaps longer visiting times with family, greater access to TV time, or self-improvement opportunities, stuff like that. Certainly I can see possible work-arounds that satisfy the public blood-lust for longer sentences, but at the same time provide a disincentive for disruptive behaviour.