Corrections costs for the states have quadrupled in the last 20 years — to about $52 billion a year nationally — making prison spending their second-fastest growing budget item after Medicaid. To cut those costs, the states must first rethink parole and probation policies that drive hundreds of thousands of people back to prison every year, not for new crimes, but for technical violations that present no threat to public safety.

According to a new study by the Pew Charitable Trusts’ Center on the States, 43 percent of prisoners nationally return to the lockup within three years. The authors estimate that the 41 states covered in the study would reap a significant savings — $635 million in the first year — if they managed to cut their recidivism rates by just 10 percent. For California’s hugely costly prison system, that would mean $233 million in savings; for New York, $42 million; and for Texas, $33.6 million.

The study, which looked at prisoner release data in 1999 and 2004, found recidivism rates varied widely. Some of the highest rates were in California (57.8 percent) and Missouri (54.4). New York is slightly under the national average (39.9 percent). Oregon had the lowest: only 22.8 percent of inmates released in 2004 returned within three years. Crime has also declined significantly.

In the 1990s, the Oregon Legislature created a rating system that allows parole officers to employ a range of sanctions — short of a return to prison — for offenders whose infractions were minor and did not present a danger. A parolee who fails a drug test can be sent to residential drug treatment or sentenced to house arrest or community service. In 2003, the state passed a law requiring all state-financed correctional treatment programs to use methods that have been shown to improve client compliance and to reduce recidivism.