After California’s prison population reached the crisis stage of overcrowding — with some prisons at 300 percent capacity — the state in 2011 began to parole thousands of inmates to their original counties. Within 15 months, more than 27,500 inmates had been “realigned” from state prisons to county jails or to parole in what was called “an act of mass forgiveness unprecedented in U.S. history.” This led to the understandable fear that suddenly returning thousands of convicts to the streets would cause a spike in crime.

It hasn’t happened.

Two detailed studies that examined crime in California, including one released last week by the journal of the American Society of Criminology, found that when considering the patterns of crime nationally and in California between 2010 and 2014, there was little or no deviation in the crime rate after the mass prisoner release. The new study, “Is Downsizing Prisons Dangerous?” by criminology professors Jody Sundt, Emily J. Salisbury and Mark G. Harmon, found that auto theft did rise somewhat in 2012 and 2013, but by 2014 it had fallen back to the norm.

“An astounding 17 percent reduction in the size of the California prison population,” Sundt’s study concluded, “had no effect on aggregate rates of violent or property crime.” The study said that California’s initial, full-throated embrace of incarceration as a means to fight crime, such as the notorious “Three Strikes” law, “may affect crime, but it does so at a high social, human and economic cost and is far less cost-effective than alternatives. Moreover, there is now evidence that prison populations can be safely reduced without harming the public.”

“Mass incarceration” has become one of the key topics in the ongoing dispute about justice reform in America. The U.S. has more inmates per capita than any other country. We have more jails than colleges. And California took its drastic steps only after ordered to do so by the Supreme Court. But since the initial realignment, California voters also approved Proposition 47, which reclassified many drug and property crimes from felonies to misdemeanors, further lightening the load on the state prison system. The fact that these studies are not finding a severe, or any, impact on crime after a mass release of prisoners adds a significant piece to the conversation about how America handles incarceration.

Sundt said in an interview Tuesday that there had not been any reports of a particularly horrible incident by a parolee from the realignment plan, which could have caused a backlash against the program. “People are really scared to make policy changes,” Bundt said, “because it just takes one horrific case” to create a new controversy.

The policy change of reducing overcrowding was mandated by the U.S. Supreme Court, which ruled in 2011 that California’s prison system amounted to “cruel and unusual punishment” and required the state to reduce its overall population from 181 percent of capacity to 137.5 percent in two years, or about 33,000 inmates. The California legislature then passed a “realignment plan” which applied only to a certain set of prisoners: those convicted of non-violent, non-sex-related and non-serious crimes.

Prisoners in the “non-non-non” group could be returned to their original counties for either time in the county jail or parole, and those who had committed violent crimes while younger than 23 could be considered for parole. Those on parole or probation would have their supervision times shortened to a maximum of six months, and parole violators would go only to jail, not back to prison. (Jails are different from prisons, and the terms are not interchangeable. Jails are run by counties or smaller municipalities and designed to hold only those awaiting trial and those sentenced to a year or less of incarceration. Prisons are run by states and intended to hold those convicted of felonies with more than a year of incarceration.)

Both a 2013 study by Magnus Lofstrom and Steven Raphael from the Public Policy Institute of California and the new Sundt study found a marked increase in auto theft after the mass releases, of as many as 130 incidents per 100,000 residents in 2012, or a 13 percent rise. But the rate rose by only 66 incidents in 2013, a seven percent rise, and no increase by 2014.

But for violent crime, “there is no evidence that the Realignment Act had an immediate effect on violent crime rates,” Sundt wrote. In 2013, as compared to 2010, there was a negligible increase in violent crime – murder, rape, robbery and aggravated assault – and in 2014, realignment was associated with a decrease of about 9.5 incidents per 100,000 residents.

Within 15 months of California passing the realignment law, savings from the reduced prison population totaled $453 million in 2012 alone, state statistics show, and “there was no adverse effect on the overall safety of Californians,” Sundt wrote.

Why didn’t crime go up? “We cannot know from this study,” Sundt wrote, “if the null findings are attributable to effective community interventions, local law enforcement, wiser use of jails, diminished returns on incarceration, or some other factors.” Sundt said in an interview that California’s legislature gave counties wide latitude in how to handle their returned prisoners, either by putting them on probation or keeping them in the county jail, and “that provided some protection for the policy makers to avoid the celebrated case that would hurt them.” Some argued that it gave county sheriffs too much power because some made decisions on whom to release and whom to keep in jail.

Sundt wrote that more money should be appropriated to study which initiatives and programs were most effective in keeping offenders from re-offending, in order to do a meaningful evaluation of “one of the largest and most dramatic public safety reforms in U.S. history.” The Sundt study also recommended that more be done to divert mentally ill offenders from the prison system, and that California, which had the highest rate of auto theft in the U.S. between 2010 and 2013, take more steps to reduce that crime.