Unauthorized Aliens Residing in the United States: Estimates Since 1986

Ruth Ellen Wasem
Specialist in Immigration Policy

Estimates derived from the March Supplement of the U.S. Census Bureau’s Current Population Survey (CPS) indicate that the unauthorized resident alien population (commonly referred to as illegal aliens) rose from 3.2 million in 1986 to 11.2 million in 2010. Jeffrey Passel, a demographer with the Pew Hispanic Research Center, has been involved in making these estimations since he worked at the U.S. Bureau of the Census in the 1980s. The estimated number of unauthorized aliens had dropped to 1.9 million in 1988 following passage of a 1986 law that legalized several million unauthorized aliens. The estimates of unauthorized aliens peaked at an estimated 12.4 million in 2007. About 39% of unauthorized alien residents in 2010 were estimated to have entered the United States in 2000 or later.

Similarly, the Department of Homeland Security’s Office of Immigration Statistics (OIS) reported an estimated 10.8 million unauthorized alien residents as of January 2010, up from 8.5 million in January 2000. The OIS estimated that 6.6 million of the unauthorized alien residents were from Mexico, an estimate comparable to Passel and D’Vera Cohn’s calculation of 6.5 million. The OIS based its estimates on data from the U.S. Census Bureau’s American Community Survey. The OIS estimated that the unauthorized resident alien population in the United States increased by 37% over the period 2000 to 2008, then leveled off in 2009 and 2010.

Research suggests that various factors have contributed to the ebb and flow of unauthorized resident aliens, and that the increase is often attributed to the “push-pull” of prosperity-fueled job opportunities in the United States in contrast to limited or nonexistent job opportunities in the sending countries. Accordingly, the economic recession that began in December 2007 may have curbed the migration of unauthorized aliens, particularly because sectors that traditionally rely on unauthorized aliens, such as construction, services, and hospitality, have been especially hard hit.

Some researchers also suggest that the increased size of the unauthorized resident population during the late 1990s and early 2000s is an inadvertent consequence of border enforcement and immigration control policies. They posit that strengthened border security has curbed the fluid movement of seasonal workers. This interpretation, generally referred to as a caging effect, argues that these policies have raised the stakes in crossing the border illegally and created an incentive for those who succeed in entering the United States to stay.

The current system of legal immigration is cited as another factor contributing to unauthorized alien residents. The statutory ceilings that limit the type and number of immigrant visas issued each year create long waits for visas. According to this interpretation, many foreign nationals who would prefer to come to the United States legally resort to illegal avenues in frustration over the delays. It is difficult, however, to demonstrate a causal link or to guarantee that increased levels of legal migration would absorb the current flow of unauthorized migrants. Furthermore, some researchers speculate that the doubling in deportations since 2001 might also have had a chilling effect on family members weighing unauthorized residence in recent years.

Some observers point to more elusive factors when assessing the ebb and flow of unauthorized resident aliens—such as shifts in immigration enforcement priorities away from illegal entry to removing suspected terrorists and criminal aliens, or discussions of possible “amnesty” legislation. This report does not track legislation and will be updated as needed.


Date of Report: September 22, 2011
Number of Pages: 17
Order Number: RL33874
Price: $29.95

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Authority of State and Local Police to Enforce Federal Immigration Law

Michael John Garcia
Legislative Attorney

Kate M. Manuel
Legislative Attorney

The power to prescribe rules as to which aliens may enter the United States and which aliens may be removed resides solely with the federal government, and in particular with Congress. Concomitant to its exclusive power to determine which aliens may enter and which may stay in the country, the federal government also has the power to sanction activities that subvert this system. Congress has defined our nation’s immigration laws in the Immigration and Nationality Act (INA), a comprehensive set of laws governing legal immigration, naturalization, work authorization, and the entry and removal of aliens. These requirements are bolstered by an enforcement regime containing both civil and criminal provisions. Deportation and associated administrative processes related to the removal of aliens are civil in nature, while certain violations of federal immigration law, such as smuggling unauthorized aliens into the country, carry criminal penalties. Congressional authority to prescribe rules on immigration does not necessarily imply exclusive authority to enforce those rules. In certain circumstances, Congress has expressly authorized states and localities to assist in enforcing federal immigration law. Moreover, there is a notion that has been articulated in some federal courts and by the executive branch that states may possess “inherent” authority to assist in the enforcement of federal immigration law, even in the absence of clear authorization by federal statute. Nonetheless, states may be precluded from taking actions if federal law would thereby be thwarted.

Recently, several states have enacted measures to facilitate the detection of unlawfully present aliens by state and local law enforcement officials. Some of these measures have been subject to legal challenge. The ability of state and local police to make arrests for federal immigration violations is a subject of ongoing legal debate and conflicting jurisprudence. Traditionally, the prevailing view has been that state and local police are permitted, to the extent allowed under state and local law, to enforce the criminal provisions of the INA. By contrast, the enforcement of the civil provisions, including the apprehension of deportable aliens, was viewed as a federal responsibility, with state and local police playing, at most, a supporting role. This view may be changing, however, as some courts have concluded that, at least in some instances, state and local police are not preempted from arresting persons on the grounds that they are deportable, even in the absence of express authorization by federal statute. The Department of Justice (DOJ) currently takes the view that state and local police are not always preempted from arresting persons for immigration violations. However, in legal challenges brought against Arizona and Alabama, it has argued that federal immigration law and policy impose some limitations upon the exercise of this authority by state and local officers.

This report discusses the authority of state and local law enforcement to assist in the enforcement of federal immigration law through the investigation and arrest of persons believed to have violated such laws. It describes federal statutes that expressly permit state and local police to enforce immigration law directly, analyzes major cases concerning the ability of states and localities to assist in immigration enforcement, and briefly examines opinions on the issue by the DOJ’s Office of Legal Counsel. This report does not directly address legal issues raised by states and localities enacting their own immigration-related laws, including measures intended to supplement federal law through the imposition of additional criminal or civil penalties. The legal implications of such measures are discussed in CRS Report R41221, State Efforts to Deter Unauthorized Aliens: Legal Analysis of Arizona’s S.B. 1070, by Kate M. Manuel, Michael John Garcia, and Larry M. Eig; and CRS Report RL34345, State and Local Restrictions on Employing, Renting Property to, or Providing Services for Unauthorized Aliens: Legal Issues and Recent Judicial Developments, by Kate M. Manuel, Jody Feder, and Alison M. Smith.


Date of Report: August 17, 2011
Number of Pages: 26
Order Number: R41423
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Unauthorized Aliens’ Access to Federal Benefits: Policy and Issues

Ruth Ellen Wasem
Specialist in Immigration Policy

Federal law bars aliens residing without authorization in the United States from most federal benefits; however, there is a widely held perception that many unauthorized aliens obtain such benefits. The degree to which unauthorized resident aliens should be accorded certain rights and privileges as a result of their residence in the United States, along with the duties owed by such aliens given their presence, remains the subject of debate in Congress. This report focuses on the policy and legislative debate surrounding unauthorized aliens’ access to federal benefits.

Except for a narrow set of specified emergency services and programs, unauthorized aliens are not eligible for federal public benefits. The law (§401(c) of P.L. 104-193) defines federal public benefit as

any grant, contract, loan, professional license, or commercial license provided by an agency of the United States or by appropriated funds of the United States; and any retirement, welfare, health, disability, public or assisted housing, postsecondary education, food assistance, unemployment benefit, or any other similar benefit for which payments or assistance are provided to an individual, household, or family eligibility unit by an agency of the United States or by appropriated funds of the United States.

The actual number of unauthorized aliens in the United States is unknown. Researchers at the Pew Hispanic Center estimate that there were 11.2 million unauthorized immigrants living in the United States in March 2010. Calculations based on the 2008 March Current Population Survey (CPS) estimated that the number of persons living in families in which the head of the household or the spouse was an unauthorized alien was 16.6 million. There were 8.8 million unauthorized families, which he defines as a family unit or solo individual in which the head or spouse is unauthorized. A noteworthy portion of the households headed by unauthorized aliens are likely to have U.S. citizen children, as well as spouses who may be legal permanent residents (LPRs), and are referred to as “mixed status” families. The number of U.S. citizen children in “mixed status” families has grown from 2.7 million in 2003 to 4.5 million in 2010. Passel estimates that one-inthree children who have a parent who is unauthorized is also considered poor according to the federal poverty rate.

Although the law appears straightforward, the policy on unauthorized aliens’ access to federal benefits is peppered with ongoing controversies and debates. Some center on demographic issues (e.g., how to treat mixed-immigration status families). Others explore unintended consequences, most notably when tightening up the identification requirements results in denying benefits to U.S. citizens. Still others are debates about how broadly the clause “federal public benefit” should be implemented.


Date of Report: September 16, 2011
Number of Pages: 24
Order Number: RL34500
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State and Local Restrictions on Employing Unauthorized Aliens

Kate M. Manuel
Legislative Attorney

In May 2011, the Supreme Court ruled in Chamber of Commerce of the United States of America v. Whiting that federal immigration law did not preempt an Arizona statute that authorized or required the suspension or termination of the licenses of businesses that knowingly or intentionally hire unauthorized aliens, and also required that employers within Arizona use the federal government’s E-Verify database to check employees’ work authorization.

The doctrine of preemption derives from the Supremacy Clause of the U.S. Constitution, which establishes that federal law, treaties, and the Constitution itself are “the supreme Law of the Land.” Thus, one essential aspect of the federal structure of government is that states can be precluded from taking actions that are otherwise within their authority if federal law is thereby thwarted. An act of Congress may preempt state or local action in a given area in any one of three ways: (1) the statute expressly states preemptive intent (express preemption); (2) a court concludes that Congress intended to occupy the regulatory field, thereby implicitly precluding state or local action in that area (field preemption); or (3) state or local action directly conflicts with or otherwise frustrates the purpose of the federal scheme (conflict preemption).

When it was enacted in 1952, the Immigration and Nationality Act (INA) did not regulate the employment of unauthorized aliens, and several states subsequently enacted measures prohibiting the employment of individuals who were not lawful residents of the United States. In a 1976 decision declining to find one such measure preempted, the Supreme Court recognized that it was “within the mainstream of [a state’s] police power” to restrict the employment of aliens within their jurisdiction whose presence in the United States was not authorized by the federal government. However, in 1986, Congress enacted the Immigration Reform and Control Act (IRCA), which amended the INA to sanction employers of unauthorized aliens and expressly preempt states and localities from sanctioning employers other than through “licensing and similar laws.” Then, in 1996, Congress enacted the Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA), which authorized the creation of a pilot program for verifying work authorization that ultimately developed into the program known as E-Verify. Under federal law, use of E-Verify by private entities is generally voluntary, and the Secretary of Homeland Security may not require persons or entities not specified in IIRIRA to participate.

Prior to the Supreme Court’s decision in Whiting, the federal courts of appeals had disagreed as to whether IRCA and IIRIRA preempted state and local measures like the Arizona statute. Some courts found that state licensing measures were within IRCA’s “savings clause” even when the state independently determined whether an employer employed unauthorized aliens, and that IIRIRA did not prohibit states from requiring use of E-Verify. Others found that such measures were preempted because the licensing provisions disrupted the balance struck by Congress between deterring illegal immigration, minimizing burdens on employers, and preventing discrimination, and Congress did not want use of E-Verify to be mandatory.

In reaching its decision, the majority in Whiting relied primarily upon the “plain meaning” of IRCA and IIRIRA, while two dissents relied more heavily upon the legislative history and overall purpose of IRCA, in particular. The majority’s decision apparently opens the door to additional state and local restrictions upon employing unauthorized aliens. However, it is unclear how closely such measures must parallel federal law to avoid being found to be preempted because they conflict with federal law, or how courts may apply the Whiting decision when reviewing other state and local immigration measures, such as those restricting access to housing or benefits.


Date of Report: September 9, 2011
Number of Pages: 17
Order Number: R41991
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Noncitizen Eligibility for Federal Public Assistance: Policy Overview and Trends

Ruth Ellen Wasem
Specialist in Immigration Policy

The extent to which residents of the United States who are not U.S. citizens should be eligible for federally funded public aid has been a contentious issue for more than a decade. This issue meets at the intersection of two major policy areas: immigration policy and welfare policy. The eligibility of noncitizens for public assistance programs is based on a complex set of rules that are determined largely by the type of noncitizen in question and the nature of services being offered. Over the past 15 years, Congress has enacted significant changes in U.S. immigration policy and welfare policy. Congress has exercised oversight of revisions made by the 1996 welfare reform law (the Personal Responsibility and Work Opportunity Reconciliation Act, P.L. 104-193)— including the rules governing noncitizen eligibility for public assistance that it established—and legislation covering programs with major restrictions on noncitizens’ eligibility (e.g., food stamps/SNAP, Medicaid).

This report deals with the four major federal means-tested benefit programs: the Supplemental Nutrition Assistance Program (SNAP, formerly food stamps), the Supplemental Security Income (SSI) program, Temporary Assistance for Needy Families (TANF) block grant programs, and Medicaid. Laws in place for the past 15 years restrict the eligibility of legal permanent residents (LPRs), refugees, asylees, and other noncitizens for most means-tested public aid. Noncitizens’ eligibility for major federal means-tested benefits largely depends on their immigration status; whether they arrived (or were on a program’s rolls) before August 22, 1996, the enactment date of P.L. 104-193; and how long they have lived and worked in the United States.

LPRs with a substantial work history or military connection are eligible for the full range of programs, as are asylees, refugees, and other humanitarian cases (for at least five to seven years after entry). Other LPRs must meet additional eligibility requirements. For SNAP, they generally must have been legally resident for five years or be under age 18. Under TANF and SSI, they generally are ineligible for five years after entry and then eligible at state option. States have the option of providing Medicaid to pregnant LPRs and children within the five-year bar. Unauthorized aliens (often referred to as illegal aliens) are not eligible for most federal benefits, regardless of whether they are means tested, with notable exceptions for emergency services, (e.g., Medicaid emergency medical care or Federal Emergency Management Agency disaster services).

TANF, SSI, food stamp, and Medicaid recipiency among noncitizens decreased over the 1995- 2005 period, but appears to have inched upwards in 2009. While the 10-year decrease was affected by the statutory changes, the poverty rate of noncitizens has also diminished over the 1995-2005 decade. The poverty rate for noncitizens residing in the United States fell from 27.8% in 1995 to 20.4% in 2005. It has risen to 25.1% in 2009. Noncitizens are disproportionately poorer than native-born residents of the United States.

This report does not track legislation and is updated as policy changes warrant.


Date of Report: August 24, 2011
Number of Pages: 29
Order Number: RL33809
Price: $29.95

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