Does illegal immigration help to reduce crime?

The Heritage Foundation recently reported some very frightening data on illegal migration and crime:

A 2021 Department of Justice report revealed that 64% of federal arrests in 2018 involved noncitizens, despite them comprising only 7% of the population at that time.

This has led the news media to obsess over crimes where an illegal migrant attacks an American citizen.  But what if this is not true?  Is it possible that illegal migration actually reduces America’s crime rate?

In a technical sense illegal migration may increase crime, at least if you view the illegal migration itself as a crime.  But is that what people are going to infer from the Heritage headline?  Or will they assume that illegal migrants are “rapists and murderers”?

I looked at the Justice Department report that the Heritage cited for its claim that illegal migrants have a high crime rate:

In 2018, 85% of federal arrests of non-U.S. citizens were for immigration offenses, and another 5% of arrests were immigration-related

Most arrests for ordinary crimes are made by state and local police officers.  Federal police are primarily responsible for addressing issues at the border:

The portion of total federal arrests that took place in the five judicial districts along the U.S.-Mexico border almost doubled from 1998 (33%) to 2018 (65%) . . . Ninety-five percent of the increase in federal arrests across 20 years was due to immigration offenses

This doesn’t mean that Heritage is wrong, just that they aren’t providing the sort of data that would allow us to evaluate the actual threat posed by illegal migrants.  The headline seems intentionally misleading.

A 2020 Cato study is somewhat more illuminating, reporting the following data for Texas:

In 2018, the illegal immigrant criminal conviction rate was 782 per 100,000 illegal immigrants, 535 per 100,000 legal immigrants, and 1,422 per 100,000 native‐​born Americans. The illegal immigrant criminal conviction rate was 45 percent below that of native‐​born Americans in Texas. The general pattern of native‐​born Americans having the highest criminal conviction rates followed by illegal immigrants and then with legal immigrants having the lowest holds for all of other specific types of crimes such as violent crimes, property crimes, homicide, and sex crimes.

In recent years, I’ve been very disappointed by the quality of the research being done by Heritage.  They seem to have latched on to the wave of populist nationalism that is sweeping the conservative movement in America.

I can’t say the Cato study is necessarily correct, but the more recent Heritage study does nothing to dissuade me from believing that illegal immigrants tend to reduce the crime rate in America.  If a group of people add 10% to the population and only 5% to the crime total, then they have effectively reduced the probability of any given American being a victim of crime.

PS.  Don’t take this post as an endorsement of illegal migration.  I’d prefer to see much higher levels of legal migration and much lower levels of illegal migration.  But much of the intense anger about illegal migration seem to have been generated by a sensationalist media that is more interested in making money than they are in accurately informing the public.

PPS.  The fact that illegal migrants have a lower than average crime rate does not mean that every subset of illegal migrants is peaceful.  It’s quite possible that illegal migrants that are from criminal gangs in Central America have a higher than average crime rate.

PPPS.  Perhaps the children of illegal migrants have a high crime rate.  But then how can we explain the relatively low murder rate in the heavily Hispanic border region of Texas?