Is There a Connection Between Undocumented Immigrants and Crime?

It’s a widely held perception, but a new analysis finds no evidence to support it.

A lot of research has shown that there’s no causal connection between immigration and crime in the United States. But after one such study was reported on jointly by The Marshall Project and The Upshot last year, readers had one major complaint: Many argued it was unauthorized immigrants who increase crime, not immigrants over all.

An analysis derived from new data is now able to help address this question, suggesting that growth in illegal immigration does not lead to higher local crime rates.

In part because it’s hard to collect data on them, undocumented immigrants have been the subjects of few studies, including those related to crime. But the Pew Research Center recently released estimates of undocumented populations sorted by metro area, which The Marshall Project has compared with local crime rates published by the F.B.I. For the first time, there is an opportunity for a broader analysis of how unauthorized immigration might have affected crime rates since 2007.

A large majority of the areas recorded decreases in both violent and property crime between 2007 and 2016, consistent with a quarter-century decline in crime across the United States. The analysis found that crime went down at similar rates regardless of whether the undocumented population rose or fell. Areas with more unauthorized migration appeared to have larger drops in crime, although the difference was small and uncertain.

(Illegal immigration itself is either a civil violation or a misdemeanor, depending on whether someone overstayed a visa or crossed the border without authorization.)

Most types of crime had an almost flat trend line, indicating that changes in undocumented populations had little or no effect on crime in the various metro areas under survey. Murder was the only type of crime that appeared to show a rise, but again the difference was small and uncertain (effectively zero).

For undocumented immigrants, being arrested for any reason would mean facing eventual deportation — and for some a return to whatever danger or deprivation they’d sought to escape at home.

There is no exact count of unauthorized immigrants living in the United States. To create estimates, experts at Pew subtracted Department of Homeland Security counts of immigrants with legal status from the number of foreign-born people counted by the Census Bureau. Many organizations and agencies, including the D.H.S., use this residual estimation method; it is generally considered the best one available. As of 2016, there were an estimated 10.7 million undocumented immigrants nationwide, down a million and a half since 2007.

Jeffrey Passel, a Pew senior demographer, and his team estimated changes in undocumented populations for roughly 180 metropolitan areas between 2007 and 2016. For comparison, The Marshall Project calculated corresponding three-year averages of violent and property crime rates from the Uniform Crime Reporting program, and the change in those rates.

The results of the analysis resemble those of other studies on the relationship between undocumented immigration and crime. Last year, a report by the Cato Institute, a libertarian think tank, found that unauthorized immigrants in Texas committed fewer crimes than their native-born counterparts. A state-level analysis in Criminology, an academic journal, found that undocumented immigration did not increase violent crime and was in fact associated with slight decreases in it. Another Cato study found that unauthorized immigrants are less likely to be incarcerated.

At the more local level, an analysis by Governing magazine reported that metropolitan areas with more undocumented residents had similar rates of violent crime, and significantly lower rates of property crime, than areas with smaller numbers of such residents in 2014. After controlling for multiple socioeconomic factors, the author of the analysis, Mike Maciag, found that for every 1 percentage point increase in an area's population that was undocumented there were 94 fewer property crimes per 100,000 residents.

More research is underway about the potential effects of undocumented immigration on crime. Robert Adelman, a professor at the University at Buffalo, SUNY, whose group’s research The Marshall Project and The Upshot have previously documented, is leading a team to expand on the Governing analysis. Early results suggest unauthorized immigration has no effect on violent crime, and is associated with lower property crime, the same as Mr. Maciag found.

Preliminary findings indicate that other socioeconomic factors like unemployment rates, housing instability and measures of economic hardship all predict higher rates of different types of crime, while undocumented immigrant populations do not.

Many studies have established that immigrants commit crimes at consistently lower rates than native-born Americans. But a common concern is whether immigrants put pressure on native-born populations in any number of ways — for instance, by increasing job competition — that could indirectly lead to more crime and other negative impacts.

According to Mr. Adelman and his team, however, the impact of undocumented immigrants is probably similar to what the research indicates about immigrants over all: They tend to bring economic and cultural benefits to their communities. They typically come to America to find work, not to commit crimes, says Yulin Yang, a member of the team.


This article was published in partnership with The Marshall Project, a nonprofit news organization covering the U.S. criminal justice system. Sign up for its newsletter, or follow The Marshall Project on Facebook or Twitter. Anna Flagg is a senior data reporter for The Marshall Project.

A version of this article appears in print on , on Page A13 of the New York edition with the headline: Undocumented Population and Crime Rate. Order Reprints | Today’s Paper | Subscribe