Donald Trump famously launched his campaign by asserting that Mexican immigrants were criminals. Now that he’s president, he’s looking to prove it.

In his first week in office, amid a flurry of executive orders targeting immigrants and asylum-seekers, he directed the Justice Department and the Department of Homeland Security (DHS) to start collecting and analyzing data on crimes committed by immigrants, as well as on the legal status of immigrants incarcerated in state and federal prisons.

The administration also pledged to publish a weekly list of crimes committed by immigrants in order to shame sanctuary cities and counties that have a policy of refusing to turn over undocumented immigrants to federal authorities.

Trump continues to repeat his claim that immigrants are a threat to American safety. He has frequently asserted, without providing evidence, that there are 2 million undocumented immigrants with criminal records in the country. Trump is not the first to make immigrants a political target. For more than a century, American nativists have argued that immigrants cause crime rates to skyrocket. The sentiment has taken deep root in the right wing: One of Trump’s biggest backers, the National Rifle Association — which spent $30 million in support of his candidacy, more than any other outside group — has used its high profile and deep pockets to stoke the populist rage that propelled Trump’s victory and which often relies on virulently anti-immigrant rhetoric.

“Latin American drug gangs have invaded every city of significant size in the United States,” NRA head Wayne LaPierre said in 2013. “Though the states on the U.S.–Mexico border may be the first places in the nation to suffer from cartel violence, by no means are they the last.”

But no data has ever supported Trump’s persistent claims that immigrants are responsible for an outsized share of crime. The research that has focused on immigrants and crime has actually concluded that immigrants are less likely to engage in criminal activity — and their presence may even make communities safer. Studies show that immigration has no effect on crime rates and that immigrants are less likely to commit crimes, or be incarcerated, than the general population. In fact, violent crime actually declines in areas where foreign-born communities have grown.

Sociologists say immigrant communities tend to be more socially cohesive than ones where nativeborn Americans predominate. Economists have suggested that the type of person who chooses to migrate tends to be less prone to criminal activity and more deterred by tough penalties than native-born citizens. The available data does not clearly differentiate between documented and undocumented immigrants, but researchers have posited that undocumented immigrants have the strongest incentives to avoid activity that would put them in contact with the criminal justice system.

Native-born Americans may be more likely to have a bad influence on immigrants than the other way around, according to a Pew Research Center analysis. First-generation immigrants are much less likely to commit a crime than Americans who have been in the country for three generations. But the crime rates of the American-born children of immigrants creep closer up to native-born whites, which one sociologist has argued is because those children assimilate into the culture. Another study found that immigrants’ incarceration rates went up the longer they had been in the United States.

Sanctuary vs. Nonsanctuary Crime Rates_002

Sanctuary cities and counties — frequent targets of Trump’s ire — have lower crime rates than other comparable areas. Law enforcement officials suggest that that might be because immigrants in sanctuary cities are less likely to view local police as a deportation force, and are more willing to cooperate with criminal investigations.

Still, anti-immigration organizations have pointed to certain statistics that paint a more dire picture. Some lawmakers and pundits have held up data from the U.S. Sentencing Commission, which found in 2015 that undocumented immigrants made up a disproportionate number of convictions for drug crimes and other offenses.

But the report doesn’t include the bulk of criminal cases in the United States, which are tried in state courts, not federal. For example, there were an estimated 15,696 murders across the country in 2015. The Sentencing Commission’s report evaluated just 91 murders — five of which were committed by immigrants.

Undocumented immigrants are also more likely to be caught up in the federal criminal justice system than citizens because of immigration violations. As of November, immigration violations made up more than half of 2016’s federal criminal prosecutions, according to Syracuse University’s Transactional Records Access Clearinghouse — meaning they are likely overrepresented in the sample.

Another popular citation by groups claiming an immigrant-driven crime wave is a 2011 GAO report that focused specifically on crimes committed by “aliens.” Mirroring the Sentencing Commission’s study, this report also measured a small subset of immigrants (just those who had been arrested); it found 296,000 immigrants in state prisons and local jails — about 0.7 percent of the total immigrant population at the time. Of these arrests the most common charges were for minor, nonviolent offenses including drugs, traffic infractions, obstruction of justice — or immigration violations.

Percentage of Criminal Aliens Arrested At Least Once by Offense Category_3

Former President Barack Obama pledged that deportations would prioritize people with criminal records — but Immigration and Customs Enforcement has struggled to find truly dangerous immigrants to remove. The most serious charge for half of the 368,644 deportees in 2013 was an immigration or traffic violation. By contrast, 12 percent of deportees had been convicted of a “serious offense” like homicide, sexual assault or robbery.

Even if the scientific data refutes Trump’s claims about immigrants, weekly lists and quarterly reports on crimes committed by immigrants will keep the dubious association alive in the public’s mind.

Clayton Mosher, professor of criminology at Washington State University and author of The Mismeasure of Crime, has warned that highlighting such data may fuel the arguments of nativists, who have already proven their willingness to cherry-pick information.

“If you’re measuring it in a problematic way, anything you derive from those data is going to be completely misleading, and in this case, potentially dangerous as well,” Mosher said.

Immigrants have committed violent crimes, and will continue to do so. But all the available research shows that claims that they pose a special threat are, in a word, bogus. There is, though, strong evidence that anti-immigrant rhetoric does pose a threat — to immigrants themselves.

After Trump was elected, reports of hate crimes soared. Latinos and Muslims — people who look foreign-born, even if they are not — have been among the most frequent targets.