(CN) - Four years after overhauling its prison system, California's prison population has decreased and violent crime has not spiked, according to a study released by the Public Policy Institute of California.
Changes made to address the state's severe prison overcrowding have "largely been successful" but recidivism rates and corrections spending continue to remain "stubbornly high," the think tank said in its report Monday.
The institute largely credits the drop in population to Proposition 47, which was passed by voters in November 2014 and reduced penalties for drug offenses and other low-level crimes.
"Since then, Proposition 47 has substantially reduced both the jail and total incarcerated populations. In the first two months after its passage, California's total incarceration rate fell to a 20-year low of 538 inmates per 100,000 residents," the report states.
The prison realignment plan was implemented in 2011 after a federal judge ordered California to decrease its notorious prison overcrowding to 137.5 percent of its combined design capacity.
California's inmate health care system has been under federal control since 2006, when the government declared California Correctional Health Care Services incapable of providing adequate treatment to inmates.
While the state met the federal prison capacity order once Proposition 47 passed, its county jails' populations rose to near historic highs. In response, counties were forced to release thousands of inmates to meet the average daily jail population capacity of 79,000.
The institute says counties will have to adapt to the influx of inmates due to Proposition 47 and provide more medical and mental health resources.
"Furthermore, even if Proposition 47 significantly reduces jail populations, these facilities will house higher shares of inmates who committed serious crimes. The changing population mix could make inmate supervision more difficult," the report found.
Critics of the state's realignment plan and Proposition 47 initially blasted the plans, predicting that the release of thousands of inmates would cause crime rates to explode. According to the study, the prison realignment did not cause violent crimes to rise but did cause a modest increase in property crimes and auto theft.
California, which imprisons more people than any other state, has historically struggled with high recidivism rates. In 2011, more than 40 percent of released inmates returned to prison within a year.
The report found that while the realignment plan aimed to slash recidivism rates, it has remained in line with pre-realignment rates. Researchers say that despite the high recidivism rates, realignment is working and counties may simply need more time do adapt the changes.
"The fact that recidivism rates have not fallen does not mean realignment has failed. First, realignment was implemented unusually quickly and counties had to prepare in a hurry. They need time to identify the most effective approaches," the report concluded.
Along with California, federal lawmakers are attempting to solve overcrowding in federal penitentiaries by reducing sentences for nonviolent offenders. On Thursday, a bipartisan group of senators announced legislation to correct decades of harsh sentencing for drug offenders and other nonviolent crimes.
"For the first time, we are cutting back many of the most severe mandatory minimums so they apply more fairly," Sen. Charles Grassley, R-Iowa said Thursday.
Grassley said the legislation, which was applauded by President Obama, could have its first hearing this month.