Fulsome prison blues

Roger Brooking has put up a piece at Pundit about “New Zealand’s strange relationship with prisons”.

In it, he highlights our imprisonment rate of 199 per 100,000 and notes that this is second only in the Western world to the United States. The problem with criticising the justice system based on the number of people in prison, is that it doesn’t take into account the effect of increased crime rates upon the prison population, nor does it account for efficient policing. If you have a lot of crime and/or a high crime resolution rate, you would expect to see that translating into a high prison populations relative to other countries, even if you’re sentencing policies were broadly similar.

Brooking also says that New Zealand’s rate of imprisonment is higher than the UK’s, even though the UK has more violent crime. This rather begs the question: if the UK has a higher rate of violent crime, ought we to be mimicking their sentencing policies? This isn’t to say that we have less violent crime simply because we imprison more people; the US also has more violent crime than we do and an even higher imprisonment rate. But, it does demonstrate that whatever the UK is currently doing is not working across the spectrum of its policies is not working as well as what New Zealand is doing, at least insofar as violent crime rates are concerned.

Brooking explains our high incarceration rate by suggesting that it is motivated by irrational fear, on the basis that our perception of safety compared to other selected countries is out of whack with our actual level of safety relative to those countries. This strikes me as a reasonable observation: public policy is often irrational – Labour’s GST and minimum wage policies spring unbidden to mind. Brooking could make his point more strongly by showing a graph of public perceptions of safety compared to actual crime victimisation rates rather than picking countries off the list. Of course, something that Brooking hasn’t accounted for is non-reporting of crime. If this were higher in New Zealand then that might explain why our level of perceived safety doesn’t gel with recorded crime rates. Brooking also fails to point out that Americans apparently feel safer but still lock more people up.

Surely, however, to determine the irrationality of our incarceration rate, some sort of cost benefit calculation is in order. Does prison cost more than the crime it prevents? The effect of incarceration on crime rates has proved difficult to determine because of the simultaneity between crime and incarceration. All else being equal, an increase in the crime rate will increase the prison population even as prisons incapacitate more criminals. This has caused studies into the effect of incarceration to reach wildly different conclusions. However, three reasonably recent studies from the US that have controlled for this simultaneity have reached very similar estimates. They conclude that for every 10% increase in the prison population, crime is reduced by 2-4%, the effect on violent crime being at the higher end of that spectrum. This effect, they conclude, is primarily due to prisons incapacitating criminals, with the rest of the effect coming from the deterrence effect on those not in prison.

So, let’s say that the cost of crime in New Zealand is $10 billion, which I’m basing on Treasury’s estimate of $9.1 billion in 2003. A 2-4% reduction in crime would save us between $200-400 million. According to Simon Power, incarcerating a prisoner costs a bit over $90,000 a year. So, a prison population of, say, 8,800 costs about $790 million a year. This is not accounting for the fact that a very high proportion of prisoners are beneficiaries, and that their benefits are stopped when they’re in prison. Increasing the prison population by 10% adds less than $80 million, which rather pales in comparison to the $200-400 million saved. So at this stage, the best research available indicates that our prisons are currently highly cost effective.

What this doesn’t prove is that prison is our best option. However, it does shift the onus back onto the Brookings of the world to demonstrate that other options are more cost effective before urging us to eschew prisons. And remember, the cost of crime is purely a cold hard statistic. Crime has a human cost too, and by indulging in the sentimental pleasure of being understanding and forgiving towards those who do society harm, we are facilitating the ongoing victimisation of the small proportion of the population that bear the brunt of crime.

The fact that many criminals continue to commit crime after being released from prison is not, in itself, a reason to stop incarcerating people. Given the high cost of crime and the relatively light cost of prison, one could just as easily argue that the precise opposite is true.


4 comments on “Fulsome prison blues

  1. Lindsay says:

    “…the US also has more violent crime than we do….”

    The available stats (US Bureau of Justice and NZ Police) don’t support this.

    (Notwithstanding comparing crime rates internationally is notoriously difficult due to multiple factors.)


    pg 17


  2. That’s interesting. If we assume that the same crimes are being measured, then we’re three times as high. That certainly doesn’t provide a lot of support for the argument that US prisons aren’t working, or that we need to lock up fewer people.

  3. I’d say instead divert policing resources currently used on war on drugs towards violent and property crime.

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