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February 6, 2018

"The Fatal Flaw in John R. Lott Jr.’s Study on Illegal Immigrant Crime in Arizona"

A few weeks ago, I posted here a link to an empirical study authored by John Lott titled "Undocumented Immigrants, U.S. Citizens, and Convicted Criminals in Arizona."  Today I saw this posting at Cato responding to Lott's study authored by Alex Nowrasteh under the title that is the title of this post.  The response claims that Lott misinterpreted the most important variable in his study, and it starts and ends this way (with links from the original):

Economist John R. Lott Jr. of the Crime Prevention Research Center released a working paper in which he purports to find that illegal immigrants in Arizona from 1985 through 2017 have a far higher prison admissions rate than U.S. citizens.  Media from Fox News to the Washington Times and the Arizona Republic have reported on Lott’s claims while Attorney General Jeff Sessions and Representative Paul Gosar (R-AZ) have echoed them from their positions of authority.  However, Lott made a small but fatal error that undermines his finding. 

Lott wrote his paper based on a dataset he obtained from the Arizona Department of Corrections (ADC) that lists all admitted prisoners in the state of Arizona from 1985 to 2017. According to Lott, the data allowed him to identify “whether they [the prisoners] are illegal or legal residents.”  This is where Lott made his small error: The dataset does not allow him or anybody else to identify illegal immigrants.

The variable that Lott focused on is “CITIZEN.”  That variable is broken down into seven categories. Lott erroneously assumed that the third category, called “non-US citizen and deportable,” only counted illegal immigrants.  That is not true, non-US citizen and deportable immigrants are not all illegal immigrants.  A significant proportion of non-U.S. citizens who are deported every year are legal immigrants who violate the terms of their visas in one way or the other, frequently by committing crimes.  According to the American Immigration Council, about 10 percent of people deported annually are Lawful Permanent Residents or green card holders — and that doesn’t include the non-immigrants on other visas who were lawfully present in the United States and then deported. I will write more about this below. 

Lott mistakenly chose a variable that combines an unknown number of legal immigrants with an unknown number of illegal immigrants.  Lott correctly observed that “[l]umping together documented and undocumented immigrants (and often naturalized citizens) may mean combining very different groups of people.”  Unfortunately, the variable he chose also lumped together legal immigrants and illegal immigrants.

The criminologist who sent me the ADC data also sent along a more detailed dataset for the stock of prisoners in Arizona for June 2017.  This newer dataset’s CITIZEN variable is just as unusable as the same variable in the 1985 to 2017 dataset but it has an additional variable that allowed us to somewhat better identify incarcerated illegal immigrants: whether the prisoner has an Immigration and Customs Enforcement (ICE) detainer....

The equivalent of the “non-U.S. citizens and deportable” variable in the June 2017 ADC database is called “criminal aliens,” another category that is not synonymous with illegal immigrants.  In Arizona’s ADC regulations, the government first determines whether a prisoner is a criminal alien and then investigates whether he or she is an illegal immigrant. In June 2017, only 38.3 percent of criminal aliens had ICE detainers on them and, thus, were more likely to be illegal immigrants.  As a back-of-the-envelope estimation, I assumed that 38.3 percent of “non-U.S citizens and deportable” are actually illegal immigrants in the ADC’s larger 1985-2017 dataset.  This back-of-the-envelope calculation turns Lott’s finding on its head.  Whereas he found that 11.1 percent of the admissions to Arizona prisons in 2014 were illegal immigrants, the real percentage is a maximum of 4.3 percent, below the 4.9 percent estimated illegal immigrant share of the state’s population. 

Lott’s controversial empirical findings regarding the high admission rate of illegal immigrants to Arizona prisons, a finding that contradicts virtually the entire body of research on the topic, stems from his simple misreading of a variable in the 1985-2017 ADC dataset.  Lott thought that “non-U.S. citizens and deportable” describes only illegal immigrants but it does not.  There is no way to identify illegal immigrants with precision in the 1985-2017 ADC dataset and their population can only be estimated through the residual statistical methods that Lott derides as “primitive.”  Using another variable in the June 2017 ADC dataset that Lott did not analyze reveals that, at worst, illegal immigrants in Arizona likely have an incarceration rate lower than their percentage of that state’s population. 

Prior related post:

February 6, 2018 at 09:51 AM | Permalink

Comments

"A significant proportion of non-U.S. citizens who are deported every year are legal immigrants who violate the terms of their visas in one way or the other, frequently by committing crimes."

To my mind this is typical academic word games. What difference does it make whether the person entered the USA legally and then committed a crime or entered the USA illegally and then committed a crime? If anything, that fact would be probative evidence that the USA's legal immigrant procedures are too weak rather than evidence that illegal immigrants are a boatload of saints.

So I don't see the mistake the author claims Lott made. If here is confusion that confusion cuts in favor of Lott, not against him.

Posted by: Selfie Man | Feb 6, 2018 12:16:36 PM

Selfie, Lott said that a group of criminals were all illegal immigrants. He based his entire study on that assumption. He claimed he didn't have to use complex statistical methods because the data had a count of illegal immigrant criminals. Turns out that count was false and included more than illegal immigrants. That means that his paper breaks.

Posted by: A | Feb 6, 2018 8:03:20 PM

The flaw in the criticism is that an ICE detainer means illegal alien. ICE catches few illegal aliens. Anyone who has called a government agency twice with the same question and gotten different answers knows, the federal government is not reliable.

Criminals do not carry ID, and use fake names. There is a lot of uncertainty.

Posted by: David Behar | Feb 7, 2018 1:36:17 PM

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