In the early 1990’s, violent crime rates in the US were reaching record levels. In response, new policies were brought in that sent more people to prison for longer periods. Over the next two decades, the US’ prison population grew dramatically while the levels of recorded crime fell to their lowest point since the 1960’s; on the face of it, it seems clear that putting more people in prison (and putting them away for longer) is what brought the crime rate down in the US. But is it that simple?
The PEW Charitable Trust decided to interview nine leading scholars for their take on the matter. And, in short, the consensus was that the relationship between imprisonment and crime is not so straightforward, and that there was likely to be many different factors that contributed to the decline in crime.
The range of possible contributing factors varies widely, and includes better policing, a declining demand for crack cocaine, the aging of the US population, more imprisonment, more jobs and an improved economy, people carrying less cash with them than they used to, anti-crime technology, more private security personnel, and a reduction in exposure to lead (which had been linked to aggressive behaviour and future crime).
But how much of an effect each factor had on the reduction in crime is difficult to measure. For example, there was some disagreement about how much of a role prison actually had in reducing the crime rate. Some suggested it had a modest effect (at best) and accounted for somewhere between 10% and 25% of the decline in crime. Others suggested it effects were more complicated than that, and that the results were still inconclusive.
Interestingly, however, there was general consensus that expanding a prison system rarely produces an equivalent decline in crime. Instead, large increases in imprisonment rates produce, at best, limited declines in crime and, as they continue to expand, may actually increase the rates of crime – a phenomenon known as ‘diminishing marginal returns’. This means that the more you continue to lock people away, the less effective prison becomes at reducing crime and after a certain point it may even lead to more crime.
In addition there was strong agreement that what deters people from crime is not how severe the punishment is, but how likely you are to get caught and how quickly you will be punished.
The brief can be read in full here.
IPRT Position Paper 6: Planning the Future of Irish Prisons.
IPRT Position Paper 3: Mandatory Sentencing.