Australia's prison population has grown about 20 per cent over the past decade, a report says.
The Productivity Commission's report on government services on Friday revealed that the national adult imprisonment rate was about 190 per 100,000 people in 2014/15, compared to 158 in 2005/06. 
The indigenous imprisonment rate per 100,000 Aboriginal and Torres Strait Islanders was higher, at 2196, compared to 139 per 100,000 non-indigenous people, it said.
Tasmania was the only state where the average daily prison population was slightly lower than five years ago, at 468 in 2014/15 compared to 474 in 2010/11.
The report also showed that government spending on prisons and community corrections grew more in the last five years at 4.3 per cent a year than for other justice services, including police and courts, to $3.7 billion in 2014/15.
The amount spent per person also grew from about $139 per person in 2010/11 compared to $156 per person in 2014/15.
Monash University Emeritus Professor Arie Frieberg said that Australia's prison population had grown steadily over the last 20 years.
"It's reflective, partly, of changed community attitudes towards crime, which judges are absorbing and getting signals from Parliament on, with increased maximum penalties, increasing restrictions on judicial discretion through mandatory sentences and a general hardening of attitudes towards crime, which is reflected in sentence lengths and, in some cases, receptions into jail," he said.
He questioned whether prisons represented a good investment: "All the evidence is that we're increasingly locking up the people with major drug (problems), mental impairment...fetal alcohol syndrome..."
University of Western Australia associate professor, Dr Hilde Tubex, said that international imprisonment rates had been rising since the 1980s. The strongest drivers for imprisonment growth in Australia were politicians' legislative changes to sentencing and the judiciary, she said.
But neither factor explained the different sizes of prison populations in various states and territories, Dr Tubex, said, with the Northern Territory's imprisonment rate about five times higher than the national average. It remained higher than the national average after you excluded indigenous prisoners, who were more likely to come into contact with the criminal justice system than the non-indigenous population due to low-socio-economic backgrounds.
"It comes down to the fact that these jurisdictions in Australia have a different penal culture, which is something that goes back in history and the way that these settlements were developed, and how and when," she said.
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