Cities that have adopted “sanctuary” policies did not record an increase in crime as a result of their decision to limit cooperation with federal immigration authorities, according to a new Stanford University report. The findings appear to rebut the Trump administration’s rhetoric about the policies’ dire effects on public safety.

The study is one of the first to measure those effects by looking at data on violent crime and property crime. Researcher David K. Hausman compared statistics across more than 200 sanctuary counties and jurisdictions between 2010 and 2015, when the policies were adopted in many U.S. cities with a large number of residents living in the country illegally.

The data show that the policies were effective at limiting deportations of nonviolent offenders but did not result in higher crime rates in those cities. And Hausman found that violent criminals continued to be deported at the same pace because the sanctuary policies do little to prevent U.S. Immigration and Customs Enforcement officials from taking those offenders into custody.

“Sanctuary policies do serve a protective role, but there’s not the cost to public safety that critics claim,” Hausman said in an interview. His findings were published in the academic journal Proceedings of the National Academy of Sciences.

ICE has targeted sanctuary jurisdictions in recent weeks with a campaign called “Operation Rise” that has led to more than 300 arrests and dovetailed with the president’s campaign attacks on Democratic mayors.

Cities and police departments that have adopted the sanctuary measures say they preserve trust between local police officers and immigrants who might be reluctant to report crimes if they fear they could be deported.

ICE officers have the authority to make immigration arrests anywhere in the United States, but sanctuary jurisdictions typically do not fulfill the agency’s requests to detain suspects long enough for ICE to pick them up at local jails. Instead, ICE officers have to find out when the suspects will be released or track them down at their homes and workplaces, requiring more time and effort.

“Sanctuary policies result in criminal aliens being released right back to the community where they can reoffend and prey upon innocent people, including our children,” interim ICE chief Tony Pham told reporters last week in Philadelphia, where the agency has put up “wanted” posters on billboards featuring the mug shots and criminal records of immigrants ICE is seeking to take into custody.

Senior Trump adviser Stephen Miller, who has written the president’s immigration policies, has repeatedly directed Homeland Security agencies to highlight violent crimes allegedly committed by immigrants.

The federal government has not backed up its broader claims with hard numbers, however, Hausman noted.

“I think it’s disappointing that the government and this administration rely on anecdotes when there is data,” he said. “The government itself keeps the data I rely on, and if the administration had looked at its own data, it would know these claims are not true.

“There’s no evidence sanctuary policies harm public safety, and there’s no evidence those policies increase crime,” added Hausman, a postdoctoral fellow who previously worked with the American Civil Liberties Union, which has led the legal opposition to the Trump administration’s immigration policies.

Hausman said data show deportations decreased by about one-third overall in jurisdictions that adopted sanctuary policies. But for immigrants who are arrested but not convicted of a crime, the sanctuary policies lowered their chances of deportation by about 50 percent.

Conversely, the policies had almost no ability to prevent the deportation of violent offenders, Hausman found. He noted that some sanctuary jurisdictions have exceptions that allow jails to comply with detainers on violent offenders. And it’s much easier for ICE to coordinate picking up immigrants with scheduled release dates from state prisons, which generally are not located in sanctuary jurisdictions.

In a statement, ICE did not directly address the findings in Hausman’s report, but the agency provided several examples of recent crimes it attributes to immigrants who had been previously released.

“U.S. Immigration and Customs Enforcement (ICE) maintains that cooperation with local law enforcement is essential to protecting public safety, and the agency aims to work cooperatively with local jurisdictions to ensure that criminal aliens are not released into U.S. communities to commit additional crimes,” ICE spokesman Mike Alvarez said. “There are numerous examples where an individual without legal status was arrested by state or local law enforcement and released into the community to reoffend while an ICE detainer was in place.”

Trump took office promising to immediately deport millions of criminals, but he never came close to doing that, averaging about 250,000 per year. ICE statistics show that the agency carried out far more deportations during President Barack Obama’s first term, when it averaged about 400,000 per year.