Illegal Immigrant Incarceration Rates, 2010–2018: Demographics and Policy Implications

President Trump has prioritized the arrest and deportation of illegal immigrants based largely on the perception that they are a significant and disproportionate source of crime in the United States.¹ According to a recent poll by the Public Religion Research Institute, 38 percent of Americans believe that immigrants increase crime in local communities; there’s little doubt that many of the responders are specifically thinking of illegal immigrants when they answer affirmatively.² Is this perception accurate? This policy analysis is the latest paper in a series that attempts to answer that question by estimating illegal immigrant incar­ceration rates in the United States by using the American Community Survey (ACS) Public Use Microdata Sample (PUMS) from the U.S. Census. This analysis goes beyond previous studies in the series as it updates our residual estimation method based on new research authored by University of California, Riverside, doctoral candidate Christian Gunadi and published in Oxford Economic Papers.³ We also apply the updated methods to estimate the illegal immigrant incarceration rates in earlier years. Gunadi’s new methods slightly increased the illegal immigrant crime rate relative to that of native‐​born Americans, but the illegal immigrant crime rate is still much lower than it is for native‐​born Americans. The data show that all immigrants—legal and illegal—are less likely to be incarcerated than native‐​born Americans relative to their shares of the population. By themselves, illegal immigrants are less likely to be incarcerated than native‐​born Americans.

We published the first nationwide estimates of the incarcerated illegal immigrant population in 2017, followed quickly by updates in 2018 and 2019.⁴ The 2017 brief analyzed incarceration rates for 2014, the 2018 brief analyzed incarceration rates for 2016, and the 2019 brief analyzed incarceration rates for 2017. The public interest in those briefs was so large that we updated the estimates using the most recent 2018 inmate data from the U.S. Census’s ACS. Estimates of the total criminal immigrant population vary widely in other sources and according to different measures, but the illegal immigrant incarceration rate is an important indicator of their criminality.⁵

Previous empirical studies of immigrant criminality generally find that immigrants do not increase local crime rates, are less likely to cause crime than their native‐​born peers, and are less likely to be incarcerated than native‐​born Americans.⁶ Illegal immigrant incarceration rates are not well studied; however, Cato Institute research based on data from the Texas Department of Public Safety found that, as a percentage of their respective populations, illegal immigrants had a criminal conviction rate about half that of native‐​born Americans in Texas in 2015 and 2017.⁷ Recent peer‐​reviewed empirical studies have found no link between violent crime and illegal immi­gration and a negative relationship between the number of illegal immigrants and most types of nonviolent crime.⁸ Our estimate of a low illegal immigrant incarceration rate is consistent with other research that finds that increasing immigration enforcement and deporting more illegal immi­grants does not reduce the crime rate, which would occur if illegal immigrants were more crime prone than natives.⁹

This policy analysis uses ACS data to estimate the incarceration rate and other demographic characteristics for immigrants aged 18–54 in 2018. ACS inmate data are reliable as they are ordinarily collected by or under the supervision of correctional institution administrators; however, the quality of the data for the population that includes the incarcerated was not always as reliable. The response rate for the group quarters population—a subpopulation who live in facilities that are owned and managed by others, which includes prisoners incarcerated in correctional facilities—was low in the 2000 census.¹⁰ Recognizing the problem with data collection from the group quarters population, the Census Bureau substantially resolved it in the 2010 census and the ACS, making several tweaks over the years that have continually improved the size and quality of the group quarters sample.¹¹

The ACS counts the incarcerated population by their nativity and naturalization status, but local and state governments rarely record whether prisoners are illegal immigrants.¹² As a result, we have to use common statistical methods to identify incarcerated illegal immi­grant prisoners by excluding prisoners with characteristics that illegal immigrants are unlikely to have.¹³ In other words, we can identify likely illegal immigrants by looking at prisoners with individual characteristics highly correlated with being an illegal immigrant.

We changed our methods for identifying illegal immigrants in this analysis. In earlier versions of this policy analysis, we identified an illegal immigrant as one who falls under these criteria: the immigrant must have entered the country after 1982 (the cutoff date for the 1986 Reagan amnesty); cannot have been in the military; cannot be receiving Social Security or Railroad Retirement Income; cannot have been covered by Veteran Affairs or Indian Health Services; is not a citizen of the United States; is not living in a household where somebody receives food stamps (unless the immi­grant’s child, who may be eligible for food stamps if a U.S. citizen, is living with the immigrant); is not from the Democratic Republic of the Congo or Syria; was aged 59 years or younger upon arrival; and is not of Puerto Rican or Cuban origin if classified as Hispanic. Further, we omitted lawfully present migrants on Temporary Protected Status (TPS) by identifying them based on their birthplace, year of migration, and citizenship status. We imputed likely TPS recipient status to individuals from El Salvador (year of arrival 2001 or earlier); Honduras (1998 or earlier); Nicaragua (1998 or earlier); Haiti (2011 or earlier); Nepal (2015 or earlier); Somalia (2012 or earlier); Sudan (2013 or earlier); South Sudan (2016 or earlier); Syria (2016 or earlier); and Yemen (2017 or earlier).¹⁴ Despite our efforts to count TPS holders as legal immigrants in those earlier briefs, some other legal immigrants whose answers were consistent with those given by illegal immigrants were counted as illegal immigrants despite their legal immigration statuses.

In this new analysis, we adjusted our identification method based on excellent recommendations by Christian Gunadi, which were published in a paper in Oxford Economic Papers.¹⁵ Whereas earlier we imputed illegal immigrant status, Gunadi imputed legal immi­grant status and identified those left over as illegal immigrants. His methods avoid the overestimation problem that we had in our earlier briefs and produce a more accurate result. Following Gunadi, we identified an immigrant as lawfully present if he or she met any of the following criteria: the immigrant arrived after 1980; is a U.S. citizen; received welfare benefits such as Social Security, Supplemental Security Income, Medicaid, Medicare, or military insurance; served in the Armed Forces; works for the government; resided in public housing or received rental subsidies or was the spouse of someone who resided in public housing or received rental subsidies; or was born in Cuba and has a spouse who is a legal immigrant or U.S. citizen. Gunadi also counted those who work in an occupation that requires some form of licensing as lawfully present, but the proliferation of licensing for illegal immigrants on the state level makes this step less useful, so we dropped it.¹⁶ Otherwise, we used Gunadi’s methods to identify legal immi­grants and identified those who remained as likely to be illegal immigrants.

A limitation of the ACS data is that not all inmates in group quarters are in correctional facilities. Although most inmates in the public‐​use microdata version of the ACS are in correctional facilities, the data also include those in mental health and elderly care institutions and in institutions for people with disabilities.¹⁷ These inclusions add ambiguity to our findings about the illegal immigrant population but not to our findings about the immigrant population as a whole, because the ACS releases macrodemographic snapshots of inmates in correctional facilities, which allows us to check our work.¹⁸

The above‐​mentioned ambiguity in illegal immigrant incarceration rates prompted us to narrow the age range to those who are aged 18–54. This range excludes most inmates in mental health and retirement facilities. Few prisoners are under age 18, many in mental health facilities are juveniles, and many of those over age 54 are in elderly care institutions. Addi­tionally, few illegal immigrants are elderly, whereas those in elderly care institutions are typically over age 54.¹⁹ As a result, narrowing the age range does not exclude many individuals from our analysis. We are more confident that our methods do not cut out many prisoners because winnowing the age range reduces their numbers in the 18–54 age range to about 4.5 percent above that of the ACS snapshot.²⁰ Natives in our results are those born as American citizens, and the group includes both those born in the United States and those born abroad to American parents.

Controlling for the size of the population is essential for comparing relative incarceration rates between the native‐​born, illegal immigrant, and legal immigrant subpopulations. Thus, we report the incarceration rate as the number of incarcerations per 100,000 members of that particular subpopulation, just as most government agencies do.²¹

An estimated 1,933,039 native‐​born Americans, 83,698 illegal immigrants, and 71,472 legal immigrants were incarcerated in 2018. The incarceration rate for native‐​born Americans was 1,477 per 100,000; 877 per 100,000 for illegal immigrants; and 380 per 100,000 for legal immigrants in 2018 (Figure 1). Illegal immigrants are 41 percent less likely to be incarcerated than native‐​born Americans. Legal immigrants are 74 percent less likely to be incarcerated than natives. If native‐​born Americans were incarcerated at the same rate as illegal immigrants, about 785,000 fewer natives would be incarcerated. Conversely, if natives were incarcerated at the same rate as legal immigrants, about 1.4 million fewer natives would be in adult correctional facilities.

The ACS data include illegal immigrants incar­cerated for immigration offenses and those in Immigration and Customs Enforcement’s (ICE) detention facilities.²² They are not incar­cerated for violent or property crimes but only for immigration violations. If we were to remove the 42,188 people in ICE detention facilities on any given day, that would lower the illegal immigrant incarceration rate to 435 per 100,000—just 15 percent above the incarceration rate for legal immigrants.²³

Because our chosen ACS variables could have affected the number of illegal immigrants we identified in the data, we altered some of the variables to see whether the results significantly changed. First, we included illegal immi­grants who lived in households with users of means‐​tested welfare benefits. Illegal immigrants do not have access to those benefits, but U.S. citizens and some lawful permanent residents in their households do. This adjustment increased the illegal immigrant incarceration rate to 1,002 per 100,000, decreased the legal immigrant incar­ceration rate to 255 per 100,000, and did not affect the native incarceration rate.

Our second robustness check excluded all immigrants who entered the United States after 2009. Immigrants on lawful permanent residency can apply for citizenship after five years, guaranteeing that most of the lawful permanent residents who are able to naturalize have done so, which decreases the pool of potential illegal immigrants in our sample. This robustness check shrinks the size of the nonincarcerated illegal immigrant subpopulation relative to those incarcerated and, thus, slightly raises the rate of illegal immigrant incarceration to about 1,061 per 100,000. These variable changes did not alter our results enough to undermine confidence in the findings.

This policy analysis uses a slightly different method than earlier studies to identify illegal immigrants. As a result, we decided to apply our new methods to previous years to give a sense of how the illegal immigrant incarceration rate has changed over time (Figure 2). In every year, the illegal immigrant incarceration rate is between 26 percent and 41 percent below that of native‐​born Americans. In every year, the legal immigrant incarceration rate is between 66 percent and 75 percent below that of native‐​born Americans. Furthermore, the incarceration rate has declined for every group. From 2010 to 2018, the native‐​born incarceration rate fell by 7 percent, the legal immi­grant incarceration rate fell by 22 percent, and the illegal immi­grant incarceration rate fell by 15 percent.²⁴

Subtracting the number of illegal immigrants in ICE detention so as to focus on more serious criminals who are likelier to pose an actual danger to public safety shows that the illegal immigrant incarceration rate is closer to that of legal immigrants in those years. From 2010 through 2018, illegal immigrants in ICE detention facilities accounted for 49–89 percent of the higher illegal immigrant incarceration rate relative to legal immigrants. In other words, the main difference between the legal and illegal immigrant incarceration rates is that illegal immi­grants are more likely to be incarcerated for violating immi­gration law.

Compared to the earlier versions, our current analysis revises the illegal immigrant incarceration rate upward by 24 percent, 21 percent, and 20 percent for the years 2014, 2016, and 2017, respectively (Figure 3).²⁵ These new revised illegal immigrant incarceration rates are still well below those for native‐​born Americans. Figure 3 shows that the illegal immi­grant incarceration rate in 2014, 2016, and 2017 was below that of native‐​born Americans by 31 percent, 36 percent, and 38 percent, respectively. That is a smaller difference than the 44 percent, 47 percent, and 49 percent that we reported in the previous respective years.

Incarceration rates vary widely by race and ethnicity in the United States, even within each immigrant category (Table 1). By race and ethnicity, legal and illegal immigrants have a lower incarceration rate than native‐​born Americans of the same race or ethnicity. The incarceration rate for all illegal immigrants is lower than the incarceration rate for native‐​born white Americans.

Immigrants from certain parts of the world are more likely to be incarcerated than others (Table 2). Of all legal immigrants, those from other countries have the highest incarceration rate. The “other” category is composed of those individuals whose country of birth is unknown or those individuals who were born at sea. Again, illegal immigrants from other countries have the highest incarceration rate of any group, followed by those from Latin America, who are most likely to be incarcerated for immi­gration offenses and held in ICE detention facilities than immigrants from any other region of the world. Across all broad groups, those born in other countries have the highest incarceration rates followed by those born in the United States. About 73 percent of all immi­grants in the United States come from the top 20 countries of origin for the foreign‐​born population.²⁶ Of those, illegal immigrants from Honduras and legal immigrants from Cuba have the highest incarceration rates (Table 3). The higher incarceration rates for illegal immi­grants from Mexico, El Salvador, Guatemala, and Honduras are likely exacerbated by the significant number of them who are detained for immigration offenses.

The distribution of prisoners by their immi­gration status and region of origin shows that 6.16 percent of all prisoners are from Latin America, whereas 92 percent were born in the United States (Table 4).

About 88.1 percent of all prisoners are men, whereas only 11.9 percent are women (Table 5). Legal and illegal immigrant women make up a smaller proportion of their respective prisoner populations than native‐​born women, while men make up a higher proportion. The sex distribution of legal immigrant prisoners is far closer to that of native‐​born Americans than to that of illegal immigrants.

Prisoners in every subpopulation are less educated than their total subpopulation (Table 6). About 63.7 percent of all native‐​born adults, including those not incarcerated, have some college education or above, whereas 18.6 percent of native‐​born prisoners have the same level of education. A total of 23.6 percent of legal immigrant prisoners and 14.4 percent of illegal immigrant prisoners have some college education or above, percentages that are lower than the percentages of their subpopulations with the same level of education (53.9 percent and 42.8 percent, respectively).²⁷ Those in every immigration category who are highly educated tend to avoid incarceration.

Native‐​born Americans and illegal immigrants have higher incarceration rates when they are young (Table 7). The peak incarceration rate for native‐​born Americans and illegal immigrants is between ages 30 and 34. The legal immigrant incarceration rate peaks between ages 25 and 29.

The incarceration rates for legal and illegal immigrants generally increase with the amount of time they have spent in the United States, the major exception being the higher legal immi­grant incarceration rate in the 0–4 years category that then falls once legal immigrants have been here for 5–9 years (Table 8). A possible reason for this phenomenon is that legal immigrants who are criminally inclined rapidly run afoul of the law, serve short prison sentences, and are removed from the United States quickly enough that the incar­ceration rate for the 5–9 years of residency category declines greatly.

Related to the amount of time immigrants have spent in the United States, illegal and legal immigrants who immigrate at a younger age are more likely to be incarcerated (Table 9). Illegal immigrants who arrive between ages 0 and 17 are about twice as likely to be incarcerated than those who arrive after age 17, suggesting that illegal immigrants who were old enough to choose to come here illegally are more law‐​abiding than those who were brought here as minors.

The pattern is even more pronounced for legal immigrants. Those who immigrated between the ages of 0 and 17 were more than twice as likely to be incarcerated than legal immigrants who came at later ages. This again suggests that those old enough to choose to come to the United States legally are more law‐​abiding.

At least two nonmutually exclusive theories can explain why those who entered in their youth have higher incarceration rates. First, spending part of one’s childhood in the United States assimilates many immigrants to our high‐​crime culture. A second theory is that those who decide to come here have some systematically different characteristics that make them less likely to commit crimes, whereas those who are too young to make the decision to immigrate do not.

The president has prioritized the arrest and deportation of illegal immigrants because much of the public believes that they are a significant and disproportionate source of crime in the United States.²⁸ For immigration in general, Gallup asked Americans whether immigration has worsened the crime problem in the United States. Some 42 percent of respondents said that immigration worsened the crime situation, 7 percent said that immigration alleviated the crime situation, and 50 percent said it had no effect.²⁹ According to Transatlantic Trends survey data, slightly less than half of Americans believe that immigrants increase crime in the United States.³⁰ Of those who believe that immigrants increase crime, about 60 percent believe that illegal immigrants are primarily responsible.³¹

Although substantial percentages of the American public believe that immigration increases crime and that illegal immigrants disproportionately contribute to the problem, the evidence is that they decrease incarceration rates in the United States. Immigrants accomplish this because they are less crime prone than native‐​born Americans. The addition of a less crime‐​prone subpopulation to the United States mechanically reduces the overall incarceration rate in the country. The facts uncovered in this policy analysis should point the government toward other immigration policies that would actually reduce crime.

For instance, federal officials should abandon efforts to convince so‐​called sanctuary cities to cooperate with federal immigration officials because such cooperation will not lower violent and property crime rates nationwide. Illegal immigrants have a lower incarceration rate than native‐​born Americans, so scarce law enforcement resources should not be spent on identifying and deporting a subpopulation with such a low crime rate. If the purpose of law enforcement is to deter crime and to punish criminals, their resources would be inefficiently allocated if targeted at illegal immigrants.

Second, the federal government already has effective programs to identify illegal immi­grant criminals who have been arrested, convicted, or incarcerated. The federal government should continue those policies and make the removal of illegal immigrant criminals a priority but should not widen their reach to include illegal immigrants who have not committed criminal offenses or have not otherwise put Americans at risk.³²

Third, the government should collect better data on illegal and legal immigrant criminality. Incarceration rates are just one measurement of criminality to fully understand relative crime rates in the United States. Unfortunately, the paucity of data means that we must estimate the number of illegal immigrants who are incar­cerated, which adds some uncertainty to our final numbers. Every state should collect and make available data on the immigration statuses of those convicted and arrested for crimes, just like Texas does, as well as those who are incarcerated.³³ To be clear, this proposal would only require documenting the immigration status of people who are arrested for crimes, convicted of crimes, or incarcerated for crimes. There is no excuse for paucity of data on this important public policy issue.

Legal and illegal immigrants were less likely to be incarcerated than native‐​born Americans in 2018, just like in 2014, 2016, and 2017.³⁴ Under the Gunadi methods that we employ here, the illegal immigrant incarceration rate rises somewhat relative to the incarceration rate for native‐​born Americas, but the gap is still huge for the period of 2010–2018.

Those incarcerated do not represent the total number of immigrants who can be deported under current law or the complete number of convicted immigrant criminals who are in the United States but merely those who are incarcerated. The younger the immigrants are upon their arrival in the United States and the longer that they are here, the more likely they are to be incarcerated as adults. This analysis provides numbers and demographic characteristics to better inform the public policy debate over immi­gration and crime. Lastly, we recommend that governments at all levels in the United States focus on collecting better data so that we can more precisely understand how illegal immigrants and legal immigrants contribute to crime in the United States.

Landgrave, Michelangelo, and Alex Nowrasteh. “Illegal Immigrant Incarceration Rates, 2010–2018: Demographics and Policy Implications.” Policy Analysis No. 890, Cato Institute, Washington, DC, April 21, 2020. https://doi.org/10.36009/PA.890.