Stephen Dinan, Washington Times, February 5, 2019

Nearly 3 percent of illegal immigrants in Arizona end up in state prison or jail during the course of a year — four times the rate of U.S. citizens and legal residents, according to a study that uses federal reimbursements for prisons and jails to try to calculate one of the most important yet elusive statistics in the immigration debate.

In New Jersey, illegal immigrants are incarcerated five times more often, and rates on the West Coast are triple that of legal residents and citizens, according to the study by the Federation for American Immigration Reform.

FAIR based its calculations on federal government reimbursements to states and localities under the State Criminal Alien Assistance Program, which pays some of the costs for holding illegal immigrants in prisons and jails. To make the payments, the federal government must determine whether an inmate is definitely or possibly in the country illegally. FAIR used the number to then calculate overall incarceration rates.

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But FAIR says the SCAAP numbers are the best calculation because they focus on those known to be arrested on criminal charges and whom federal officials have concluded are in the country illegally.

In the 10 states FAIR selected, they determined that illegal immigrants ended up behind bars at higher rates, per capita.

“This study should put to rest, once and for all, the notion that illegal aliens commit crimes at a lower rate than legal residents,” FAIR President Dan Stein said. “By focusing on states with significant illegal alien populations and that consistently report to the SCAAP program, FAIR’s study refutes this erroneous claim.”

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The group took a snapshot of the prison population in a state, using data from the Prison Policy Initiative, then subtracted the number of illegal immigrants the federal government paid to incarcerate in a year. That provided numbers for both an illegal immigrant prison population and everyone else.

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{snip} FAIR estimates that Arizona has an illegal immigrant population of 365,950 and non-illegal-immigrant population of 6.7 million. Incarceration rates were 2.815 percent for illegal immigrants and 0.702 percent for all others.

That means one out of every 35 illegal immigrants in Arizona was in state prison or jail in 2016, which was the highest rate of any of the states they studied.

They did the same calculations for nine other states that have strong SCAAP reporting and account for about three-quarters of the estimated illegal immigrant population in the country.

In each of the 10 states, they found illegal immigrants incarcerated at higher rates. The gap was biggest in New Jersey, with an illegal immigration jail rate 440 percent higher, followed by Arizona, Oregon, Washington and California in the top five.

New York and Nevada came next, with rates at least 160 percent higher, followed by Florida, Texas and New Mexico, with the smallest gap — though even there, illegal immigrants were 42 percent more likely to be in prison or jail than the citizen and legal resident population.

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Mr. Lott’s research [John R. Lott Jr., president of the Crime Prevention Research Center], using data from Arizona that differentiates between immigrants, found that legal immigrants had the lowest rates of incarceration, with citizens in the middle and illegal immigrants with the highest rates of crime.

“FAIR here has stuff from multiple states indicating that if in fact they’re right on all this, it’s pretty much systematically true across all prison systems and jail systems,” he said.

But Alex Nowrasteh, a senior immigration policy analyst at the Cato Institute, questioned FAIR’s methodology. He said the data used to calculate the overall prison population doesn’t link up with the SCAAP data, so trying to make incarceration comparisons doesn’t work.

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The SCAAP data that FAIR used doesn’t delve into the specific crimes covered, so it’s impossible to say from the data whether one population tended toward more serious offenses compared with the other.

Other potential problems with the SCAAP data include the risk of double-counting because the numbers give only an aggregate of inmate stays. If someone is in a local jail and then a state prison for the same offense in the same year, then they could be double-counted.

FAIR, though, says the conditions of SCAAP money — someone must have a felony or two misdemeanor convictions — plus the average length of stay means the rate of double-counting is likely small.

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Among homicides in particular, of 785 convictions in Texas in 2015, 709 were native-born, legal immigrants were 30 and illegal immigrants were 46. That works out to rates of 3.1 per 100,000 for native-born, 1 per 100,000 legal immigrants and 2.6 per 100,000 illegal immigrants.