Yeah lets add a source and some context to that:
Passed in 2006, Italy's Collective Clemency Bill presents a unique opportunity to study the deterrent effect of prison sentences, the authors say. Crime rates often drop when criminal penalties are increased. But it's often hard to tell if the rates go down because the threat of longer sentences deters potential criminals, or if the drop happens because actual criminals are physically removed from the street for longer periods. This study of the clemency law's effects eliminates the latter scenario, measuring only deterrent effect.
When the clemency bill was passed, it immediately released thousands of prisoners who had three years or less left on their sentences. The remainder of each prisoner's sentence was suspended, but not forgiven. The law stipulated that a former inmate who commits a new crime within five years will have the suspended portion of his sentence reinstated and added to the sentence for the new crime. As a result, a repeat offender can expect extra jail time equal to the suspended portion of his sentence—anywhere from one month to three years.
[...]
"This means that a policy a commuting actual sentences in expected sentences significantly reduces recidivism," Dr. Vertova says. "A mass release of prisoners can be effective in reducing their propensity of re-committing crimes if, when a released individual gets convicted of a new crime, his normal sentence is increased by the time that was pardoned because of the early release."
There was one important exception to the deterrent effect, however. Recidivism rates among those whose original crime was more serious were essentially unaffected by the length of their suspended sentence. That finding suggests that "more dangerous inmates are not deterred," the authors write.
The researchers also caution that their results only measure deterrence on those who have already served time in jail. "Indeed, it is not clear whether these results can be to individuals who have never received prison treatment."
When the clemency bill was passed, it immediately released thousands of prisoners who had three years or less left on their sentences. The remainder of each prisoner's sentence was suspended, but not forgiven. The law stipulated that a former inmate who commits a new crime within five years will have the suspended portion of his sentence reinstated and added to the sentence for the new crime. As a result, a repeat offender can expect extra jail time equal to the suspended portion of his sentence—anywhere from one month to three years.
[...]
"This means that a policy a commuting actual sentences in expected sentences significantly reduces recidivism," Dr. Vertova says. "A mass release of prisoners can be effective in reducing their propensity of re-committing crimes if, when a released individual gets convicted of a new crime, his normal sentence is increased by the time that was pardoned because of the early release."
There was one important exception to the deterrent effect, however. Recidivism rates among those whose original crime was more serious were essentially unaffected by the length of their suspended sentence. That finding suggests that "more dangerous inmates are not deterred," the authors write.
The researchers also caution that their results only measure deterrence on those who have already served time in jail. "Indeed, it is not clear whether these results can be to individuals who have never received prison treatment."

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