The report, released today by the Pew Center on the States, said the 50 states spent more than $49 billion on corrections last year, up from less than $11 billion 20 years earlier. The rate of increase for prison costs was six times greater than for higher education spending, the report said.
Using updated state-by-state data, the report said 2,319,258 adults were held in U.S. prisons or jails at the start of 2008 -- one out of every 99.1 adults, and more than any other country in the world.
The steadily growing inmate population "is saddling cash-strapped states with soaring costs they can ill afford and failing to have a clear impact either on recidivism or overall crime," said the report.
Susan Urahn, managing director of the Pew Center on the States, said budget woes are prompting officials in many states to consider new, cost-saving corrections policies that might have been shunned in the recent past for fear of appearing soft in crime.
"We're seeing more and more states being creative because of tight budgets," she said in an interview. "They want to be tough on crime, they want to be a law-and-order state -- but they also want to save money, and they want to be effective."
The report cited Kansas and Texas as states which have acted decisively to slow the growth of their inmate population. Their actions include greater use of community supervision for low-risk offenders and employing sanctions other than reimprisonment for ex-offenders who commit technical violations of parole and probation rules.
"The new approach, born of bipartisan leadership, is allowing the two states to ensure they have enough prison beds for violent offenders while helping less dangerous lawbreakers become productive, taxpaying citizens," the report said.
While many state governments have shown bipartisan interest in curbing prison growth, there also are persistent calls to proceed cautiously.
"We need to be smarter," said David Muhlhausen, a criminal justice expert with the conservative Heritage Foundation. "We're not incarcerating all the people who commit serious crimes -- but we're also probably incarcerating people who don't need to be."
According to the report, the inmate population increased last year in 36 states and the federal prison system.
The largest percentage increase -- 12 percent -- was in Kentucky, where Gov. Steve Beshear highlighted the cost of corrections in his budget speech last month. He noted that the state's crime rate had increased only about 3 percent in the past 30 years, while the state's inmate population has increased by 600 percent.
The Pew report was compiled by the Center on the State's Public Safety Performance Project, which is working directly with 13 states on developing programs to divert offenders from prison without jeopardizing public safety.
"For all the money spent on corrections today, there hasn't been a clear and convincing return for public safety," said the project's director, Adam Gelb. "More and more states are beginning to rethink their reliance on prisons for lower-level offenders and finding strategies that are tough on crime without being so tough on taxpayers."
The report said prison growth and higher incarceration rates do not reflect a parallel increase in crime or in the nation's overall population. Instead, it said, more people are behind bars mainly because of tough sentencing measures, such as "three-strikes" laws, that result in longer prison stays.
"For some groups, the incarceration numbers are especially startling," the report said. "While one in 30 men between the ages of 20 and 34 is behind bars, for black males in that age group the figure is one in nine."
The nationwide figures, as of Jan. 1, include 1,596,127 people in state and federal prisons and 723,131 in local jails -- a total 2,319,258 out of almost 230 million American adults.
The report said the United States is the world's incarceration leader, far ahead of more populous China with 1.5 million people behind bars. It said the U.S. also is the leader in inmates per capita (750 per 100,000 people), ahead of Russia (628 per 100,000) and other former Soviet bloc nations which make up the rest of the Top 10.