Much of the debate surrounding the federal crackdown on undocumented immigrants centers on the notion that they pose a threat to public safety. It’s a viewpoint that has persisted for years, long before Donald Trump made it a hallmark of his presidential campaign and began signing executive orders ramping up immigration enforcement.

A large body of research, however, finds no link between immigration and high crime rates, with some studies suggesting places with more immigrants actually enjoy slightly lower crime rates. Still, critics often contend that illegal immigration leads to more crime as research has generally failed to distinguish such individuals from the vast majority of legal immigrants who've been vetted by authorities.

To shed light on this contention, Governing conducted an analysis using recently released metro area population estimates from the Pew Research Center for “unauthorized immigrants” -- people who crossed the border illegally or overstayed visas. The analysis not only found no link with violent crime, but indicated concentrations of unauthorized immigrants were associated with marginally lower violent crime rates. A statistically significant negative correlation was also shown for property crimes. For every 1 percentage-point increase in the unauthorized immigrant share of a metro area’s population, average property crime rates dropped by 94 incidents per 100,000 residents.

Estimates of undocumented immigrants and average annual crime rates over a three-year period for 154 metro areas were analyzed in a regression model, controlling for a dozen socioeconomic variables. Pew’s unauthorized immigrant population estimates are the first set of regional-level figures the center has published. Nationally, they suggest this demographic accounts for a quarter of foreign-born residents, or about 3.5 percent of the total U.S. population.

Our analysis of the Pew data, while limited to a narrow time period, mirrors findings of broader academic research dismissing a relationship between foreign-born residents, regardless of legal status and higher crime rates. “The literature is pretty clear,” says Robert Adelman, an associate professor at the State University of New York (SUNY) at Buffalo. “Results are strong and stable across time and place.”

A recent study Adelman co-authored in the Journal of Ethnicity in Criminal Justice found increases in total foreign-born populations over time were associated with reductions in robberies, murder rates and all types of property crimes across metro areas. Some individual studies have reported contrary evidence, but they are in the minority. A forthcoming paper in The Annual Review of Criminology reviews more than 50 studies, finding that 2.5 times as many studies indicate a negative correlation between immigration and crime as those suggesting the opposite effect. Incarceration rates depict similar patterns, with an analysis by the advocacy group American Immigration Council reporting immigrant males ages 18 to 39 are incarcerated at roughly half the rate of native-born residents.

Despite decades of research casting doubt on any connection, emphasis on public safety risks that immigrants could pose remains a frequent talking point in the push to bolster immigration enforcement. In his joint address to Congress this week, Trump called attention to homicides where undocumented immigrants have been charged. One of the president's executive orders creates a new office, Victims of Immigration Crime Engagement (VOICE), to study such crimes and publish a weekly list of “criminal actions committed by aliens and any jurisdiction that ignored or otherwise failed to honor any detainers with respect to such aliens.”

Undocumented immigrants, the main focus of the current federal policy debate, remain concentrated in few regions. According to Pew, they are most common in smaller Western and Southwestern metro areas such as McAllen-Edinburg-Mission, Texas; Salinas, Calif.; and Yuma, Ariz., where they account for about a tenth of all residents.

It's these same places that tend to record relatively low crime rates. The 20 metro areas where unauthorized immigrants were most prevalent in the Governing analysis recorded, on average, property crime rates 10 percent lower and violent crime rates 8 percent lower than those of all other regions reviewed. El Paso and San Diego, both adjoining the Mexican border, post some of the lowest violent crime rates of any big American cities year after year, for example.

Metro Area Group Unauthorized Share of Population Average Property Crimes per 100k Average Violent Crimes per 100k Average Murders per 100k
Top 20 Highest % of Unauthorized Immigrants 6.5%-10.3% 2,591.9 375.9 4.3
All Other Metro Areas 0.2%-6.4% 2,884.5 408.1 4.8
SOURCE: Governing calculations of Pew Research Center, FBI 2013-2015 annual crime rates.

Most studies associating immigrants with declining crime rates claim the effects are modest. While there's no single explanation for a causal link, experts suggest immigrants could make neighborhoods safer in a number of ways. Many scholars point to the role they play in opening new businesses or buying up previously abandoned properties. “They bring a social and economic vitality to metro areas that benefits those areas,” Adelman says.

Another common explanation suggests their desire to secure employment and avoid deportation makes them less inclined to engage in criminal behavior. Of course, immigrants' backgrounds and the circumstances surrounding their arrival vary. Harvard sociologist Robert Sampson theorizes that a diffusion of cultures, with immigrants migrating from countries where violence carries different meanings, may help to limit crime across society. “Immigration and the increasing cultural diversity that accompanies it generate the sort of conflicts of culture that lead not to increased crime but nearly the opposite,” he writes.

It’s possible that some immigrants are simply hesitant to report incidents to police, suppressing crime rates. However, a recent study in the Journal of Quantitative Criminology suggests otherwise. Researchers compared self-reported arrests to official accounts for offenders over a seven-year period, finding the foreign born accurately reported their arrests at rates statistically identical to those of their native-born peers. Additionally, murder rates, one type of crime nearly always reported, weren't correlated with unauthorized immigrant populations in the Governing analysis.

It's also important to note that estimates of those not residing in the country legally, particularly for smaller regions, are difficult to pin down. Pew computed its estimates for unauthorized immigrants by subtracting known lawful immigrant totals from foreign-born survey estimates.

Houston Police Chief Art Acevedo says his experience serving in different departments aligns with research suggesting immigrants don’t commit crimes any more frequently than natives. It’s important, he says, for law enforcement to reach out to immigrant communities, as some new arrivals fear police from prior negative experiences in their home countries. “We spend a lot of time immersing ourselves in these communities to build trust and hopefully reduce skepticism,” says Acevedo, who frequently appears on local Spanish media. “We need to not do anything to hinder the trust that we’ve taken decades to build.”

Part of the Trump administration's immigration enforcement push proposes potentially withholding federal funds from so-called sanctuary cities like Houston. Yet a recent analysis by a University of California, San Diego, professor found crime to be lower in sanctuary counties, or those not accepting detainers.

Although mounting evidence rejects any link between immigration and additional crime, public notions of immigrants as hardened criminals persist.

Half of U.S. adults in a 2015 Pew Research Center survey said immigrants make the crime problem worse, compared to just 7 percent who believed they make it better. Another study conducted at Arizona State University found the perceived size of the undocumented immigrant population was more associated with views of undocumented immigrants as criminal threats than actual numbers of immigrants or economic conditions. "There's a long history in our country of immigrants being scapegoated for all sorts of things," says Monica Varsanyi, a John Jay College of Criminal Justice associate professor. "They are easy targets."

Read the complete analysis


Metro Area Data

SOURCE: Crime rates are 2013-2015 annual average rates per 100,000 residents calculated from the FBI's Uniform Crime Reporting data. Unauthorized immigrant totals were published by the Pew Research Center and represent estimates for 2014.