A University of Buffalo study looking at 40 years of data between 1970 and 2010 found there wasn't a link between increased immigration and increased crime.
Instead, the study found some types of crime had lessened as immigration increased.
"Our research shows strong and stable evidence that, on average, across U.S. metropolitan areas crime and immigration are not linked," said UB sociology professor Robert Adelman, the paper’s lead author, in a university press release. "The results show that immigration does not increase assaults and, in fact, robberies, burglaries, larceny, and murder are lower in places where immigration levels are higher."
He added: "The results are very clear."
The authors looked at U.S. Census Bureau data from 200 metropolitan areas, as well as uniform crime reporting data from the Federal Bureau of Investigation between 1970 and 2010. During that same time, the total numbers of immigrants in the U.S. have quadrupled, from 9.6 million in 1970 to 42.4 million in 2014, according to the Migration Policy Institute.
"The most striking finding from our research is that for murder, robbery, burglary and larceny, as immigration increased, crime decreased, on average, in American metropolitan areas," Adelman wrote in the Scientific American. "The only crime that immigration had no impact on was aggravated assault. These associations are strong and stable evidence that immigration does not cause crime to increase in U.S. metropolitan areas, and may even help reduce it."
Adelman pointed out that aim of this study, which included researchers from the University of Alabama, Georgia State University and Kennesaw State University, was not to argue that increased immigration didn't produce crime. But the numbers do appear to indicate that there is not necessarily an increase.
"This is a study across time and across place, and the evidence is clear," Adelman said. "We are not claiming that immigrants are never involved in crime. What we are explaining is that communities experiencing demographic change driven by immigration patterns do not experience significant increases in any of the kinds of crime we examined. And in many cases, crime was either stable or actually declined in communities that incorporated many immigrants."