In 136 metro areas, almost 70 percent of those studied, the immigrant population increased between 1980 and 2016 while crime stayed stable or fell. The number of areas where crime and immigration both increased was much lower — 54 areas, slightly more than a quarter of the total. The 10 places with the largest increases in immigrants all had lower levels of crime in 2016 than in 1980.
And yet the argument that immigrants bring crime into America has driven many of the policies enacted or proposed by the administration so far: restrictions to entry, travel and visas; heightened border enforcement; plans for a wall along the border with Mexico. This month, the Justice Department filed a lawsuit against California in response to the state’s restrictions on local police to assist Immigration and Customs Enforcement officers in detaining and deporting undocumented immigrants charged with crimes. On Tuesday, California’s Orange County signed on in support of that suit. But while the immigrant population in the county has more than doubled since 1980, overall violent crime has decreased by more than 50 percent.
There’s a similar pattern in two other places where Mr. Trump has recently feuded with local leaders: Oakland, Calif., and Lawrence, Mass. He described both cities as breeding grounds for drugs and crime brought by immigrants. But Oakland, like Orange County, has had increasing immigration and falling crime. In Lawrence, though murder and robbery rates grew, overall violent crime rates still fell by 10 percent.
In general, the study’s data suggests either that immigration has the effect of reducing average crime, or that there is simply no relationship between the two, and that the 54 areas in the study where both grew were instances of coincidence, not cause and effect. This was a consistent pattern in each decade from 1980 to 2016, with immigrant populations and crime failing to grow together.