For the first time since the Depression, the prison population has shown a sustained drop – and is on track to tumble further.
In the past decade the prison population grew by 45.6 per cent – but the latest annual Justice Sector Forecast predicts that in the next 10 years it will fall by 6.2 per cent.
The decrease is being attributed to a falling crime rate and to new police tactics that have seen fewer people brought before the courts.
Corrections Department spokesman Brendan Anstiss said: "There are ups and down in the forecast each year and each month, but in modern history this is the first sustained drop.
"It's a big change – when you see that we've been growing for 80-odd years and now it's stabilising and now ... predicting a drop."
In May, Finance Minister Bill English said no more prisons would be built under his watch, calling them a "moral and fiscal failure".
"The public service has done a lot of very smart work on this and over the next two or three years we're going to see the need for prison beds drop a bit at least," he said at the time.
The latest forecast also says the number of prosecutions, for both summary and committal cases, will decrease over the next decade, as fewer people enter the court system.
Last month, Wellington District Court moved to change its courtroom timetables after a drop in cases meant the main judges' list would fail to use the whole day allotted to it.
Police Deputy Commissioner Mike Bush said part of the drop in cases could be attributed to a more pro-active approach to stopping crime before it happened and the introduction of the "alternative resolution initiative".
Alternative resolution allows police to use their discretion and give people warnings or diversion when they face low-level charges, such as breaches of liquor bans or disorderly behaviour, if deemed appropriate.
"We're actually making more arrests but we're putting less people in front of the courts. It's the opposite of us going soft – we're just dealing with people in different and more effective ways."
The resolution process meant staff could spend more time on the street, instead of preparing prosecution files and appearing in court for very low-level crimes, Mr Bush said.
"It also means for young and first-time offenders that we can do something other than putting them straight on to the justice treadmill which can lead them right to a life of crime."
Victoria University criminology Professor John Pratt said past politicians' choices had been inflating the prison population for years and had been locking up too many people.
"I'm certain that's the case. You've only got to look at comparative prison rates for societies similar to New Zealand – we lock up many more people than they do in England, Australia.
"I think they [past governments] have been far too prepared to invest in imprisonment without thinking about the long-term consequences of what they were doing and also the huge social and financial costs of that sort of policy.
"The more people you can stop going to prison, the less chance they have of being seduced into the world of crime which is rife in those prisons."
Corrections Minister Judith Collins said the falling crime and prison population rates were a "dramatic drop".
"The people who should be in prison are in prison, but we don't want low-level offenders in prison if there is a better way of dealing with them. It's a very expensive option and we know that the younger they are when they end up in prison the more likely they are to stay there for a very long time.
"If we can keep people out of the justice system but still deal with the offences ... that's going to have a far better outcome."
Too Many Prisons?
New jails built in recent years, such as Springhill Prison and Northland Prison, have not simply created extra beds and will not be wasted, the Corrections Department's Brendan Anstiss says.
"The prisons that we have built in the last few years have been designed to help with rehabilitation.
"You need to treat the person and address the causes of crime and you can do that better in a modern purpose-built facility than what you can in a place which was designed to break rocks and to punish."
The future of older prisons, such as Wellington's Mt Crawford, would not be affected immediately by the forecast.
"The department is always working to make sure we have the prison facilities we need.
"The yearly Criminal Justice Forecast is one of a number of factors and tools that we use to inform our long-term planning and we will be analysing the latest forecast carefully."
- The Dominion Post
What do you make of the proposed conference centre/hotel for Wellington?Related story: Convention centre to get OK