The Departments of Justice and Homeland Security (DOJ/DHS) will be publishing a quarterly report on immigrant incarceration in federal prisons because of an Executive Order issued by President Trump last year. The most recent report found that 20 percent of all inmates in federal prison are foreign-born and about 93 percent of them are likely illegal immigrants. Since immigrants are only about 13.5 percent of the population and illegal immigrants are only about a quarter of all immigrants, many are misreading it and coming away with the impression that foreign-born people are more crime-prone than natives. 

That is simply not true.

This new DOJ/DHS report only includes those incarcerated in federal prisons, which is not a representative sample of all incarcerated persons in the United States. Federal prisons include a higher percentage of foreign-born prisoners than state and local correctional facilities because violations of immigration and smuggling laws are federal offenses and violators of those laws are incarcerated in federal prisons. 

The report itself almost admits as much with this important disclaimer: 

This report does not include data on the alien populations in state prisons and local jails because state and local facilities do not routinely provide DHS or DOJ with comprehensive information about their inmates and detainees—which account for approximately 90 percent of the total U.S. incarcerated population.

There is much better information on immigrant incarcerations in other formats. My co-author Michelangelo Landgrave and I recently released a Cato brief that estimates incarceration rates by immigration status in federal, state, and local correctional facilities. We used a standard statistical technique known as the residual method to identify illegal immigrants in the incarcerated population in the American Community Survey in 2016. We found that illegal immigrants are 47 percent less likely to be incarcerated than native-born Americans and legal immigrants are 78 percent less likely to be incarcerated than natives. The results reported in our recent brief are similar to our other research into immigrant incarceration and conviction rates as well as the peer-reviewed academic research.

The evidence that legal and illegal immigrants are less likely to be incarcerated, convicted, or even arrested for crimes is so overwhelming that even immigration restrictionists like Mark Krikorian at the Center for Immigration Studies admit that, “A lot of data does suggest immigrants are less likely to be involved in crime.”

Crime data in the United States is poor, especially as it relates to details about the immigration status of the offenders. There is no good reason for a dearth of data on this topic. Thus, improving the quality of crime and immigration data is important so that we can better understand the relationship between immigration and criminality. Unfortunately, the new DOJ/DHS report does not help because the information it presents is of a non-representative subsample of the entire incarcerated population, the title of the report strongly suggests that it reports all incarcerations rather than just those in federal correctional facilities, and this information is already available.