HELENA - Montana will see the fastest prison population growth rate in the nation over the next five years unless it changes its current sentencing and prisoner release practices, a study released Wednesday predicted.

Nine of the top 10 states with the fastest projected inmate population growth rates are in the West.

The report, published by the Public Safety Performance Project of The Pew Charitable Trusts, predicted that Montana's prison population to grow by 41 percent from 2006 to 2011. Most other Western states - including Washington, Wyoming, Idaho, Utah, Nevada, New Mexico, Colorado, Arizona, Alaska and Hawaii - are projected to see an inmate population

increase of at least 20 percent. Nationally, state prison populations are projected to increase 12 percent, the report found.

Nationwide, the report said, one in every 178 Americans will live in prison by 2011.

The report used data from 42 states to predict prison growth rates. Most states used complex mathematical models to predict their prison growth rate. Some, like Montana, used a more simple method that examines past trends to predict future inmate growth. Researchers had to estimate the growth rates for the eight other states that did not provide any future predictions.

Dr. James Austin, a criminologist and one of the report's authors, said the larger prison population estimates in the West are due in part to the region's overall population gains, which outpace national averages.

But tougher sentencing and more difficult prison-release requirements have also contributed to the increases, Austin said. Arizona, for example, requires its prisoners to serve at least 85 percent of their sentences and has limited its available options to deal with the rising prisoner population, he said. Arizona ranked second behind Montana with a projected prison population increase of 35 percent by 2011.

Austin also noted that many mandatory prison sentences do not differentiate between violent prisoners and those who pose little risk to public safety. They also squelch the incentive for a prisoner to take part in rehabilitation programs that could lead to lower recidivism rates, he said.

"It doesn't make any sense to have a system that is called the department of corrections if there's no corrections going on," Austin said.

In Montana, the state Department of Corrections has been well aware of its rapidly growing prisoner population and Gov. Brian Schweitzer has made increasing the state's budget for corrections to include more rehabilitation programs one of his priorities this legislative session.

Adam Gelb, director of the project that commissioned the report, said he think Schweitzer's efforts could, if successful, reduce the projected prison growth rate. The governor has proposed a $100 million increase in the Corrections budget.

"It seems like they are focused on trying to stop the revolving door," Gelb said.

But on Wednesday, House Republicans shelved Schweitzer's proposed budget after a brief hearing.

The Pew report, Anez said, underscores the need for legislators to realize the consequences of cutting the budget for programs that provide alternatives to prison.

"There's a reason why we asked for them," Anez said. "That's because we see this growth in the prison population."