More than one in every 100 American adults is in jail or prison — making the United States the world's incarceration leader, according to a new report tracking the surge in U.S. inmate population.

The report, released Thursday by the Pew Center on the States, urged U.S. states to curtail corrections spending by placing fewer low-risk offenders behind bars.

"The United States imprisons more people than any country in the world," the report said. Using updated state-by-state data, it said more than 2.3 million adults were held in U.S. prisons or jails at the start of 2008 — or one of every 99.1 adults out of a total population of some 230 million adults.

The numbers put the United States far ahead of more populous China, which it said has 1.5 million people behind bars, and Russia, which has 890,000. The Pew report cited January statistics from the "World Prison Brief" released by the International Center for Prison Studies at London's King's College.

It also said the U.S. — with 750 inmates per 100,000 people — "is the global leader in the rate at which it incarcerates its citizenry, outpacing nations like South Africa and Iran."

South Africa has 341 per 100,000 citizens, Iran has 222 per 100,000, and China 119, according to the World Prison Brief.

Russia and other former Soviet republics had the highest incarceration rates in Europe. Russia has 628 inmates per 100,000 people, followed by Belarus' 426 per 100,000, Georgia's 401 per 100,000 and Ukraine's 345 per 100,000, according to the World Prison Brief.

Within the United States, the 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," the report said.

The 50 states spent more than US$49 billion (euro32.4 billion) on corrections last year, up from less than US$11 billion (euro7.3 billion) 20 years earlier, the report said. On average, states spend 6.8 percent of their general funds on corrections, the report said.

The rate of increase for prison costs was six times greater than for higher education spending, the report said. Four states — Vermont, Michigan, Oregon and Connecticut — now spend more on corrections than they do on higher education.

"These sad facts reflect a very distorted set of national priorities," said Sen. Bernie Sanders, an independent from Vermont.

Susan Urahn, managing director of the Pew Center on the States, said many states were considering new cost-saving corrections policies.

"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 ... but they also want to save money."

Kansas and Texas, for example, have started using more community supervision for low-risk offenders and sanctions other than re-imprisonment for those who commit technical violations of parole and probation rules, the report said.

Last year, 36 states as well as the federal prison system recorded increases in prison populations, the report said. The largest percentage increase — 12 percent — was in Kentucky.

Kentucky Gov. Steve Beshear last month noted that, for the past 30 years, the state's crime rate had increased only about 3 percent while the number of inmates went up 600 percent.

The Pew report was compiled by the Center on the State's Public Safety Performance Project, which is working with 13 states on developing programs to divert offenders from prison.

The report said the higher incarceration rates did 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.

The numbers were "especially startling" for some groups, 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 racial disparity for women also is stark. One in 355 white women aged 35-39 is behind bars, compared with one in 100 black women in that age group.

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 of 2,319,258.