Introduction

Congress has a long-standing interest in the unauthorized immigrant population. Unauthorized immigrants are noncitizens (aliens under the law)¹ who generally have entered the United States without inspection, overstayed a period of lawful admission (overstays), or violated the terms of their admission. The population is also referred to by different adjectives by various observers, including undocumented, irregular, and illegal.²

The size and composition of the U.S. unauthorized population has changed over time in conjunction with a multitude of factors, including global economic and origin country conditions, U.S. labor market demand, U.S. immigration policy and border enforcement, migrant networks, and changing fertility in sending countries.³ Although the unauthorized population is challenging to measure directly, as described below, analysts have documented notable changes in its size and composition over time.

As of the cover date of this report, an estimated 11 million unauthorized immigrants reside in the United States.⁴ Estimates suggest the unauthorized population has decreased from its peak of approximately 12 million in 2007. Prior to 2010, most immigrants became unauthorized by entering the United States without inspection, a flow dominated by Mexican nationals. In recent years, flows of migrants crossing the Southwest border without inspection have increasingly included migrants from Central America. Simultaneously, there has been an increase in return migration to Mexico by unauthorized Mexican immigrants. In addition, in recent years, more individuals from countries other than Mexico or those in Central America have entered the unauthorized population by overstaying their period of lawful admission. As a result, the national origins of unauthorized immigrants—once overwhelmingly represented by Mexican nationals—have become more diverse.

This report provides answers to frequently asked questions about the unauthorized immigrant population, addressing topics including the population size and demographics; eligibility for benefits, voting, and military service; economic characteristics; impact on crime rates; pathways to and legislative proposals for permanent legal status; and interior immigration enforcement such as removal, among other topics. The report's scope is limited to the population already residing in the United States; therefore, it does not address policies or issues related to migrant arrivals at the border.⁵

Population Size and Demographics

How many unauthorized immigrants live in the United States?

There are no direct measures of the unauthorized population residing in the United States. The federal government does not have official counts of unauthorized immigrants living in this country in administrative data. Major government population surveys, such as the decennial census and American Community Survey (ACS), do not collect information on respondents' immigration status.⁶

Nevertheless, researchers in academic settings, nongovernmental research organizations, and federal agencies have developed estimates of the unauthorized population using available survey data. These estimates rely on various methodologies that impute immigration status based on other characteristics captured in government surveys—principally, the ACS, as well as administrative records from the Department of Homeland Security (DHS). Recent estimates from authoritative sources within the last five years vary, but generally place the unauthorized population between approximately 10 million and 11 million individuals. Table 1 enumerates the most recent unauthorized population estimates from six sources.

Based on these estimates, the unauthorized population represents about 23% to 26% of the approximately 44.1 million foreign-born individuals living in the United States.⁷

There is a general consensus among researchers that the unauthorized population grew during the 1980s, 1990s, and early 2000s until it reached a peak of approximately 12 million around 2007.⁸ The population then declined following the Great Recession.⁹ Some researchers estimate that the unauthorized population has declined in recent years¹⁰ while others estimate that the population has stabilized.¹¹ Recent estimates also suggest that the proportion of all foreign-born individuals who are unauthorized has generally declined.¹²

How do people become unauthorized?

The unauthorized population generally¹⁸ consists of individuals in the United States who entered without inspection (EWI) and those who overstayed a period of a lawful admission or violated the terms of their admission.¹⁹ While the majority of the total unauthorized population are people who entered without inspection, in recent years overstays have accounted for the majority of the newly unauthorized population. For example, an analysis of unauthorized migration from 2010 to 2017 found that the majority of individuals who became unauthorized during that period were overstays.²⁰ An estimated 46% of the total unauthorized population in 2017 were overstays.²¹ The proportion of overstays has increased primarily because EWIs began to decline after 2000.²²

Where are unauthorized immigrants from?

Mexican nationals have long represented the largest national group of unauthorized immigrants in the United States. Recent estimates place Mexican nationals at between 46% and 48% of the total unauthorized population.²³ However, this proportion has generally declined in recent years as a substantial number of migrants have returned to Mexico while unauthorized migration from countries other than Mexico has increased.²⁴ For example, migrants from Central America and Asia have made up a growing proportion of the unauthorized population.²⁵ After Mexico, top countries of origin for the unauthorized population residing in the United States in 2018-2019 were El Salvador, Guatemala, India, Honduras, and China.²⁶

How long have unauthorized immigrants lived in the United States?

As of 2019, a relatively large proportion of unauthorized immigrants—estimates range from 58% to 62%—had lived in the United States for at least a decade. Approximately 22%-23% had lived in the United States for 20 years or more, 16%-17% for 5 to 9 years, and 21%-25% for fewer than 5 years.²⁷

Where do unauthorized immigrants live in the United States?

Unauthorized immigrants live in all 50 states and the District of Columbia. As of 2019, states with the largest unauthorized immigrant populations included California, Texas, New York, Florida, New Jersey, and Illinois.²⁸ Since the early 2000s, unauthorized migrants—along with the foreign-born more generally—have become more dispersed from traditional immigrant gateways (e.g., California, Texas, New York) to new immigrant destinations, including areas in the Southeast (e.g., North Carolina, Georgia, and Virginia).²⁹

How many unauthorized immigrants are members of mixed-status families?

Mixed-status is a general term that refers to a family whose members may have different citizenship and/or immigration statuses. Examples include spouses with different immigration or citizenship statuses and/or children with different statuses than their parent(s). Many unauthorized immigrants are members of mixed-status families, although the exact number is unknown and depends on how mixed-status is measured in a given study.

Estimates from 2019 show that approximately 45% of unauthorized immigrants ages 15 and older were married. Among those who were married, about 41% had an LPR or U.S. citizen spouse.³⁰ About 41% of unauthorized immigrants ages 15 and older resided with at least one child under age 18. The majority of this group (81%) resided with at least one child who was a U.S. citizen.³¹ According to 2018 estimates, 5.2 million children ages 17 and under (7% of the total U.S. child population) lived with at least one unauthorized immigrant parent. Eighty-five percent of those children were U.S. citizens.³²

Eligibility for Certain Federal and State Benefits

Are unauthorized immigrants eligible for federal public benefits?

Unauthorized immigrants are not eligible for most federal benefits. This includes programs such as non-emergency Medicaid,³³ the Supplemental Nutrition Assistance Program (SNAP),³⁴ Supplemental Security Income (SSI),³⁵ Temporary Assistance for Needy Families (TANF),³⁶ and most housing assistance programs.³⁷

In some instances, unauthorized immigrants are eligible for specific types of federal benefits, including the following benefits for which statutory exceptions were outlined in Title IV of the Personal Responsibility and Work Opportunity Reconciliation Act of 1996 (PRWORA, P.L. 104-193): emergency Medicaid; short-term, in-kind disaster relief; immunization against and treatment for communicable diseases; certain services and assistance designated by the Attorney General;³⁸ and certain housing programs if the noncitizens were receiving assistance on the date PRWORA was enacted.³⁹

Additionally, PRWORA states that individuals who are eligible for public education benefits under state and local law shall remain eligible to receive benefits under the National School Lunch Program and School Breakfast Program.⁴⁰ Beyond these nutrition programs, Section 742 of the act neither prohibits nor requires a state to provide food assistance to unauthorized immigrants through certain laws. This applies to programs such as the Child and Adult Care Food Program; the Summer Food Service Program; the Special Supplemental Nutrition Program for Women, Infants, and Children; the Emergency Food Assistance Program; the Commodity Supplemental Food Program; and the Food Distribution Program on Indian Reservations.

Does federal law restrict unauthorized immigrants' access to state public benefits?

Although PRWORA expressly bars unauthorized immigrants from most state and locally funded benefits, the law allows states through enactment of new state laws to provide unauthorized immigrants with state and local benefits that, if not for the new laws, would be restricted.⁴¹

PRWORA's restrictions on state benefits parallel the restrictions on federal benefits.⁴² Unauthorized immigrants are generally barred from state and local assistance, government contracts, licenses, grants, and loans. The exceptions to the restrictions on state benefits also parallel the exceptions made for federal benefits discussed above, including treatment for emergency conditions; short-term, in-kind emergency disaster relief; immunization against and treatment for communicable diseases; and certain services and assistance designated by the Attorney General.⁴³

Also, the PRWORA restrictions on state and local benefits do not apply to activities that are funded in part by federal funds; these activities are regulated under PRWORA's provisions on federal benefits. Furthermore, the law states that nothing in it is to be construed as addressing eligibility for basic public education.

Can unauthorized immigrants receive work authorization?

Generally, unauthorized immigrants are not eligible for work authorization. In some cases, individuals with certain statuses or pending applications may be eligible for work authorization. DACA recipients may apply for work authorization from DHS. TPS recipients are granted work authorization by virtue of their status.⁴⁴ For DED, eligibility for work authorization depends on the terms the President specifies in each DED designation.⁴⁵ Asylum applicants may apply for work authorization 150 days after filing an application for asylum.⁴⁶ As of 2021, certain U visa⁴⁷ applicants and qualifying relatives (including those who may be unauthorized) with pending petitions may receive work authorization.⁴⁸

Are unauthorized immigrants eligible for student aid and/or in-state tuition?

Unauthorized immigrants are not eligible for federal student aid.⁴⁹ They may be eligible for state financial aid, college financial aid, or private scholarships, based on the rules of the relevant entities. Unauthorized immigrants may be eligible for in-state tuition in some states based on state-specific policies.

Are unauthorized immigrants eligible for driver's licenses and REAL IDs?

In general, issuance of and eligibility requirements for driver's licenses are matters of state law and policy. As of September 2021, unauthorized immigrants are able to get driver's licenses in 16 states, the District of Columbia, and Puerto Rico.⁵⁰

The REAL ID Act (P.L. 109-13) established minimum security standards for state-issued driver's licenses and identification cards required for certain federal purposes (e.g., to board domestic flights and access certain federal facilities). This includes evidence that the individual has "lawful status"⁵¹ in the United States. Thus, unauthorized immigrants are not eligible for REAL IDs. States may still issue identification cards or driver's licenses that are noncompliant with REAL ID, but those IDs may not be used for the specified federal purposes.

Eligibility for Voting and Military Service

Are unauthorized immigrants eligible to vote in elections?

All non-U.S. citizens, including unauthorized immigrants, are ineligible to vote in federal elections. The Illegal Immigration Reform and Immigrant Responsibility Act of 1996 (P.L. 104-208, Division C, §216) introduced criminal penalties for noncitizens who vote in federal elections. The law specifies that noncitizens may vote in non-federal elections as authorized by states and localities. Some localities have permitted noncitizens to vote in local elections.⁵²

Are unauthorized immigrants eligible to serve in the U.S. military?

In general, unauthorized immigrants may not enlist in the U.S. Armed Forces. By law, enlistment is open to U.S. citizens, lawful permanent residents, noncitizen nationals (e.g., individuals born in American Samoa and Swains Island), and persons from Micronesia, the Marshall Islands, and Palau.⁵³

Service Secretaries within the Armed Forces are statutorily authorized to enlist a limited number of other persons who possess critical skills or expertise deemed "vital to the national interest."⁵⁴ From 2008 through 2016, the Military Accessions Vital to the National Interest (MAVNI) Program permitted the enlistment of certain noncitizens whose medical skills and language expertise were deemed vital to the national interest. However, the Department of Defense (DOD) required those enlistees to have lawful presence. Eligible populations included asylees, refugees,⁵⁵ nonimmigrants,⁵⁶ those with TPS, and DACA beneficiaries.⁵⁷ The MAVNI program was suspended in 2016 following DOD's establishment of new security screening requirements.

Economic Characteristics

Because measures of immigration status are generally not available in major government survey data, it is difficult to disaggregate the economic impacts of unauthorized immigrants from the economic impact of immigrants more generally. Such estimates are more widely available for the foreign-born population. Where possible in this section, CRS has included estimates related to the unauthorized population specifically. In other cases, information is limited to the foreign-born population broadly.

At what rate do unauthorized immigrants participate in the labor force?

The labor force participation rate is the proportion of individuals ages 16 and older in the civilian labor force who are employed or are unemployed and actively seeking work. The foreign-born tend to have higher rates of labor force participation compared with those born in the United States. This trend has long been documented by the Bureau of Labor Statistics (BLS).⁵⁸ BLS reported that in 2021, the foreign-born labor force participation rate was 64.7%, compared with 61% for the native-born. Labor force participation is particularly high among foreign-born men. In 2021, 76.8% of foreign-born men participated in the labor force, compared with 65.8% of native-born men. Foreign-born women, conversely, have lower rates of labor force participation than native-born women (53.4% and 56.6%, respectively).⁵⁹

Unauthorized immigrants, specifically, participate in the labor force at higher rates than the foreign-born population broadly and the native-born population. In 2019, estimates of unauthorized immigrants' labor force participation ranged from 69% to 77%.⁶⁰ Unauthorized immigrant men tend to have even higher labor force participation rates.⁶¹

In which industries do unauthorized immigrants work?

Unauthorized immigrants are highly concentrated in certain industries, including agriculture, construction, leisure/hospitality, services, and manufacturing.⁶² An analysis of 2016 data, for example, found that unauthorized immigrants comprised 5% of the total civilian labor force but 15% of the agriculture industry, 13% of the construction industry, and 8% of the leisure/hospitality industry.⁶³ Certain occupations within those industries also have particularly high concentrations of unauthorized workers. For example, a Department of Labor survey of U.S. farmworkers in FY2019-FY2020 found that 44% of hired crop workers were unauthorized.⁶⁴ Industry concentration varies by U.S. geography.⁶⁵

Do unauthorized immigrants impact the wages of U.S.-born workers?

A 2017 summary report by the National Academies of Sciences, Engineering, and Medicine (NASEM report) states that empirical evidence on the wage impacts of foreign-born workers "reveals one sobering reality: Wage and employment impacts created by flows of foreign-born workers into labor markets are complex and difficult to measure."⁶⁶

Because of data limitations, few studies have examined the impacts of unauthorized immigrants, specifically, on the wages of U.S.-born workers. Empirical studies of wage impacts instead tend to focus on other foreign-born worker subgroups, especially education or skill level. Unauthorized workers are generally assumed to be concentrated in unskilled jobs. The NASEM report's review of the literature explains the centrality of worker complementarity versus worker substitution with regard to the impacts of newly arrived immigrants:

For cases in which immigrants and natives specialize in different occupational activities [i.e., worker complementarity] ... wage gains and job creation become likely outcomes. When new arrivals compete with those already in the labor force—for example, if unskilled immigrants and native-born teenagers (or earlier immigrants) are applying for the same fast food restaurant jobs [i.e., worker substitution]—wages and job opportunities for the latter may be negatively impacted, at least in the short run.

In general, the NASEM report finds that among low-skilled workers, foreign-born workers' negative impacts on the wages of U.S.-born workers tend to be more pronounced in the short run and are very small over periods of more than 10 years. The groups that were most likely to experience wage declines associated with new immigrant arrivals to the low-skilled labor market were previous cohorts of immigrants and native-born individuals lacking a high school diploma.⁶⁷

What fiscal impacts do unauthorized immigrants have on federal, state, and local governments?

Research on fiscal impacts generally considers the difference between public expenditures on the benefits and services immigrants receive and the tax revenues they contribute (e.g., via income taxes). The NASEM report contends that fiscal impacts generally reveal themselves over several years because an individual's contributions and program expenditures change across the course of his or her life.

NASEM's analysis finds that among the foreign born, fiscal impacts are generally positive at the federal level and negative at state and local levels. For example, state and local governments assume most costs of public education. The analysis also finds that foreign- and native-born persons similarly matched on characteristics like age and education "will likely have about the same fiscal impact."⁶⁸

Similar to the wage impacts described above, data limitations make it difficult to isolate public expenditures and tax contributions for unauthorized immigrants, specifically. Nevertheless, immigration status is likely an important determinant of fiscal impact. As described previously (see the "Eligibility for Certain Federal and State Benefits " section), unauthorized immigrants are ineligible for most public benefits; however, states may not deny children a free public education because of their immigration status.

In considering the economic characteristics of unauthorized immigrants, NASEM states that because unauthorized immigrants tend to be younger than other foreign-born groups, and therefore more likely to be in the labor market, and because they are ineligible for many public benefits, they may have a more positive fiscal impact at the federal level compared with other immigrant groups. However, they also note that unauthorized immigrants tend to have lower earnings than other foreign-born groups and may therefore have lower tax contributions.⁶⁹

Are unauthorized immigrants required to pay federal taxes?

Unauthorized immigrants may be required to pay federal taxes (e.g., if they work in the United States). However, quantifying their contribution is difficult, as unauthorized immigrants generally do not have a special designation under tax law and do not provide information as to whether they are lawfully present on federal tax documents such as the federal income tax return. Hence, the Internal Revenue Service (IRS) does not have official estimates of the federal taxes paid by unlawfully present noncitizens in the United States or the tax benefits they claim.

For federal tax purposes, unauthorized immigrants are treated like any other noncitizens and are categorized as either resident or nonresident aliens.⁷⁰ This designation—which is for federal tax purposes only—is based on the time they reside in the United States and not their immigration status. It is neither an indication of immigration status, nor does it affect immigration status. Resident aliens are generally taxed in the same manner as U.S. citizens. Nonresident aliens are subject to different treatment, such as generally being taxed only on income from U.S. sources.

In addition, by law, individuals must provide a unique identifying number when they file tax returns and other documents with the IRS.⁷¹ Generally, an individual's taxpayer identification number is his or her Social Security number (SSN). However, certain noncitizens are not eligible for SSNs, including unauthorized immigrants.⁷² Individuals who are not eligible to receive an SSN are required to use an individual taxpayer identification number (ITIN) when filing their documents, such as tax returns, with the IRS.⁷³ ITINs are issued by the IRS and are for federal tax purposes only. Use of an ITIN does not necessarily mean an individual is unlawfully present.⁷⁴ However, the IRS and the Treasury Inspector General for Tax Administration believe that a large proportion of ITIN filers are unlawfully present noncitizens working in the United States.⁷⁵

Crime

Is there a relationship between unauthorized immigrants and crime?

Assessing the relationship between unauthorized immigration and crime is complicated by, among other challenges, data limitations and the inability to compare research studies that use different methods, evaluate different populations, cover different periods, and/or ask different research questions.

Nevertheless, ample research on immigration and crime consistently indicates that, in general, immigrants have either no impact or a reductive impact on crime.⁷⁶ This has been seen in individual studies as well as studies that review bodies of literature on immigration and crime.⁷⁷

Likewise, most empirical scholarship examining the relationship between unauthorized immigrants, specifically, and crime have similar findings. For example, studies have found that unauthorized immigration does not increase violent crime, and in some cases it decreases such crime.⁷⁸ Other studies show unauthorized immigration is associated with a reduction in drug arrests, drug overdoses, and driving under the influence.⁷⁹ Some studies have also shown that unauthorized immigration reduces rates of property crime, larceny, and burglary.⁸⁰

Pathways to Permanent Status

Are unauthorized immigrants able to obtain permanent legal status?

There are limited options for unauthorized immigrants to gain permanent legal status.⁸¹ To adjust to LPR status from within the United States under the main adjustment of status provision in the INA (§245(a)),⁸² an individual must have been inspected and admitted or paroled into the United States. Those who enter the United States unlawfully fail to meet this requirement. In addition, noncitizens must have maintained lawful status since entering the United States. This would mean that noncitizens who had been inspected and admitted but overstayed a period of lawful admission would not be eligible for LPR status.⁸³

Certain LPR pathways are available to individuals regardless of unlawful entry or unlawful presence. Asylum may be granted to individuals in the United States who are unable or unwilling to return to their country of nationality because of persecution or a well-founded fear of persecution on account of race, religion, nationality, membership in a particular social group, or political opinion. There are no numerical limitations on asylum grants.⁸⁴ Asylees may adjust to LPR status after one year of physical presence in the United States.⁸⁵

Other LPR pathways, which account for relatively few immigrants due to numerical limitations, include U nonimmigrant visas for noncitizen crime victims who assist law enforcement agencies, T status for noncitizen victims of human trafficking,⁸⁶ and cancellation of removal for noncitizens in removal proceedings.⁸⁷

What are the three- and ten-year bars?

Immigration law also contains restrictions for certain individuals who leave the United States and subsequently apply for an immigrant visa from abroad. Noncitizens who were unlawfully present in the United States for between 6 and 12 months are considered inadmissible to the United States for three years, and those unlawfully present for more than one year are inadmissible for ten years (often referred to as the three- and ten-year bars).⁸⁸ These bars are triggered when the individual leaves the United States. Waivers are available for those who are the spouse, son, or daughter of a U.S. citizen or LPR if "refusal of admission to such immigrant alien would result in extreme hardship to the citizen or lawfully resident spouse or parent of such alien."⁸⁹

Are unauthorized immigrants able to become U.S. citizens?

In general, to be eligible for U.S. citizenship through the naturalization process, applicants must first obtain LPR status (see "Are unauthorized immigrants able to obtain permanent legal status?"). LPRs may choose to naturalize upon meeting certain eligibility criteria—typically, after five years in LPR status (or three if married to a U.S. citizen).⁹⁰ Expedited pathways are available to noncitizen members of the U.S. Armed Forces.⁹¹

Naturalization is optional for LPRs—an estimated 9.2 million are currently eligible to naturalize but have not done so.⁹² Naturalized citizens gain certain benefits, including the right to vote, security from deportation in most cases, access to certain public sector jobs, and the ability to travel with a U.S. passport.

What legalization programs for unauthorized immigrants have been proposed in recent Congresses?

At several points during the past 20 years, Congress has considered legislation to establish pathways to LPR status for certain groups of foreign nationals in the United States, including certain unauthorized immigrants. These bills have focused largely, but not exclusively, on persons without a lawful immigration status. Past measures have included stand-alone bills with pathways to LPR status for unauthorized childhood arrivals (these bills typically have been referred to as Dream Acts)⁹³ as well as bills proposing broader changes to the immigration system that included LPR pathways for different groups.

In the 117^th Congress, proposed LPR pathways have been focused on several overlapping groups: unauthorized childhood arrivals (commonly referred to as Dreamers), individuals with TPS or DED, agricultural workers, and individuals deemed essential workers during the COVID-19 pandemic.⁹⁴

Removal

How many unauthorized immigrants are in removal proceedings?

Noncitizens may be placed in removal proceedings based on grounds of inadmissibility or deportability.⁹⁵ These grounds may apply to both unauthorized immigrants and those with lawful immigration status (e.g., LPRs; nonimmigrants). During removal proceedings, an immigration judge determines whether the noncitizen is removable (deportable), and if so, whether they are eligible for forms of relief from removal, such as asylum. Removal proceedings begin when noncitizens are issued a Notice to Appear (NTA) charging document and it is filed with an immigration court.⁹⁶

As of June 2022, an estimated 1.8 million noncitizens were in removal proceedings in immigration courts, a large portion of whom were unauthorized immigrants.⁹⁷ Within that group, approximately 1.1 million individuals were charged with entry without inspection and an additional 663,000 were charged with another immigration infraction, such as violating the conditions of an authorized stay.⁹⁸ Some may ultimately be granted relief from removal during their proceedings.

How many unauthorized immigrants are deported every year?

DHS is responsible for immigration enforcement in the United States, including apprehending noncitizens who are removable (deportable) because they have violated immigration laws and removing from the United States noncitizens with a final order of removal.

Noncitizens may be removed through different types of processes, including the following:

• when an immigration judge issues an order of removal during formal removal proceedings;⁹⁹
• under expedited removal, in which arriving aliens¹⁰⁰ and migrants who recently entered the United States without inspection may be removed by DHS without formal proceedings in immigration court;
• under reinstatement of final removal orders for noncitizens who have re-entered the United States without authorization after a previous removal or voluntary departure; and
• under administrative removal for noncitizens convicted of an aggravated felony who did not have LPR status when their removal proceedings commenced.

Immigration and Customs Enforcement (ICE), within DHS, is responsible for immigration enforcement in the U.S. interior.¹⁰¹ From FY2011 through FY2020, DHS removed an annual average of 96,373 individuals apprehended by ICE.¹⁰² Not all of those removed are unauthorized immigrants. Lawfully present noncitizens (e.g., LPRs) may be subject to removal for certain reasons (e.g., criminal offenses).

Whom should I contact with additional questions?

For more information on the topics covered in this report, contact the CRS experts listed in the Key Policy Staff table below.