Neighbourhoods across the United States that experienced a growth in their undocumented population also saw property-related and violent crime fall, not rise, according to an analysis of 11,500 neighbourhoods in more than 100 cities.

In a paper published in the Journal of Urban Affairs on 10 August¹, researchers combined estimates of numbers of undocumented residents with crime statistics between 2010 and 2018.

“Our study is the first to analyse these numbers across neighbourhoods and using such a diverse national sample,” says co-author Charis Kubrin, a criminologist at the University of California, Irvine. “That’s important because neighbourhoods are very proximate spaces to people. That’s where perceptions form.”

Earlier studies “have used samples of people or places in a specific jurisdiction,” says Alexis Piquero, a criminologist at the University of Miami in Coral Gables, Florida, but the new work has “a much larger reach”.

The findings support previous research that did not find a link between immigration and violent crime in the United States and elsewhere. “That very much fits the picture that we’ve seen in UK studies,” says Ben Brindle, a senior researcher with the Migration Observatory project at the University of Oxford, UK.

In the neighbourhood

Undocumented immigrants include people who entered the country illegally or who reside there on an expired visa. The public perception of them is often fuelled by the belief that they are more likely to commit crimes than are documented immigrants or citizens.

But, Piquero notes, “it’s very hard to measure the number of undocumented immigrants in any country because they’re undocumented. So, researchers have come up with estimates.”

In the current study, Kubrin and her colleagues were granted access to non-public demographic data for 46 million people through a US federal statistical research data center.

To estimate the number of undocumented immigrants, the researchers excluded people who were recorded to be US citizens or born in the country, as well as those who were recorded as receiving public health insurance, enrolled in higher education or married to a US citizen — because these individuals are likely to be authorized visa holders or permanent residents.

The analysis found that, on average, 5.6% of residents in a neighbourhood were undocumented in 2010, and that this dropped to 4.8% in 2018. “Our estimates are quite similar to [those of] the Department of Homeland Security,” says Kubrin.

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The researchers then mapped the proportion of undocumented immigrants across neighbourhoods, using crime data from the National Incident Crime Study. Kubrin and her colleagues focused on violent crimes — which included homicides, robberies and aggravated assaults — as well as the property crimes such as burglaries and motor-vehicle thefts.

Their analysis revealed that increases in undocumented immigrant populations were associated with lower levels of property crimes and aggravated assaults.

Robberies, however, tended to increase in neighbourhoods with increased undocumented populations. “It could be that crime rates are higher in some neighbourhoods because immigrants are victims rather than offenders,” says Kubrin. Undocumented immigrants are more likely to get paid in cash and less likely to have bank accounts than are other residents, which could put them at a greater risk of being robbed, for instance.