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.