Unauthorized Aliens Residing In United States: Estimates Since 1986 – Analysis

By Ruth Ellen Wasem

The number of foreign-born people residing in the United States (an estimated 37 to 39 million) is at the highest level in our history and, as a portion of the U.S. population, has reached a percentage (12.4%) not seen since the early 20th century.1 The actual number of unauthorized aliens in the United States is unknown. Of the foreign-born residents in the United States, approximately one-third are to be estimated unauthorized aliens residents (often characterized as illegal aliens), one-third are estimated to be legal permanent residents (LPRs), and one-third are estimated to be naturalized U.S. citizens.2

The three main components of the unauthorized resident alien population are (1) aliens who overstay their nonimmigrant visas,3 (2) aliens who enter the country surreptitiously without inspection, and (3) aliens who are admitted on the basis of fraudulent documents. In all three instances, the aliens are in violation of the Immigration and Nationality Act (INA) and subject to removal.
The last major law that allowed unauthorized aliens living in the United States to legalize their status was the Immigration Reform and Control Act (IRCA) of 1986 (P.L. 99-603). Generally, legislation such as IRCA is referred to as an “amnesty” or a legalization program because it provides LPR status to aliens who are otherwise residing illegally in the United States. Among IRCA’s main provisions was a time-limited legalization program, codified at § 245A of the Immigration and Nationality Act, that enabled certain illegal aliens who entered the United States before January 1, 1982, to become LPRs.4 It also had a provision that permitted aliens working illegally as “special agricultural workers” to become LPRs.5 Nearly 2.7 million aliens established legal status through the provisions of IRCA.

Continued high levels of unauthorized migration to the United States have, in part, prompted the current discussion of guest worker programs, as well as major proposals that would permit legalization under specified conditions. There are also proposals aimed at reducing unauthorized migration by tightening up enforcement of immigration laws. The report of the National Commission on Terrorist Attacks Upon the United States (also known as the 9/11 Commission) stated that “more than 9 million people are in the United States outside the legal immigration system” as one of the reasons for the Commission’s recommendations to improve immigration services and strengthen enforcement of immigration laws.6

This CRS report presents data estimating the number of unauthorized aliens who have been living in the United States since 1986. There have been a variety of estimates of the unauthorized resident alien population over this period, sometimes with substantially different results. This report is limited to data analyses of the Current Population Survey (CPS)7 conducted by the U.S. Census Bureau and the Bureau of Labor Statistics and the American Community Survey (ACS)8 conducted by the U.S. Census Bureau so that there are basic standards of comparison over time.9 Because the CPS and the ACS are both sample surveys of the U.S. population, the results are estimates. Additionally, while the data distinguish between the foreign born who have naturalized and those who have not, they do not identify immigration status (e.g., legal permanent resident, refugee, temporary foreign worker, foreign student, unauthorized alien). Summaries of the detailed analyses of the March CPS, the ACS, and the monthly CPS are presented separately because each of these surveys is based on different questions and sample sizes.

Estimates Since 1986

For a basis of comparison, Figure 1 presents the estimate of 3.2 million unauthorized resident aliens in 1986 calculated by demographers Karen Woodrow and Jeffrey Passel, who worked for the U.S. Census Bureau at that time. As expected after the passage of IRCA, the estimate for 1988 dropped to 1.9 million.10 According to demographer Robert Warren of the former Immigration and Naturalization Service (INS), the estimated unauthorized resident alien population grew to 3.4 million in 1992 and to 5.0 million in 1996.11 By the close of the decade, the estimated number of unauthorized alien residents had more than doubled. Passel, now at the Pew Hispanic Center, estimated the unauthorized population in 2000 at 8.5 million, but this latter estimate included aliens who had petitions pending or relief from deportation.12

Subsequently, Warren estimated that there were 7.0 million unauthorized aliens residing in the United States in 2000. As depicted in Figure 1, he also revised his earlier analyses using the latest CPS and estimated that there were 3.5 million unauthorized aliens living in the United States in 1990 and 5.8 million in 1996. Warren excluded “quasi-legal” aliens (e.g., those who had petitions pending or relief from deportation) from his estimates.13 By 2002, the estimated number of unauthorized resident aliens had risen to 9.3 million.14 During the first decade after IRCA, researchers projected that the net growth in unauthorized aliens had averaged about 500,000 annually; analyses done during the early 2000s estimated the average growth at 700,000 to 800,000 unauthorized alien residents annually.15

The estimated number of unauthorized alien residents peaked in 2007, when Passel estimated that there were 12.4 million unauthorized alien residents in the United States (Figure 1). The confidence intervals around the 12.4 million estimate ranged from a low of 11.9 million to a high of 12.9 million. “Thus, average annual growth over the 5-year period since 2000 was more than 500,000 per year. This number reflects the number of new unauthorized migrants arriving minus those who either die, return to their country of origin, or gain legal status.” 16

Michael Hoefer, Nancy Rytina, and Bryan C. Baker of the Department of Homeland Security’s (DHS’s) Office of Immigration Statistics (OIS) published their 2007 estimates of the unauthorized resident alien population from the American Community Survey (ACS) of the U.S. Census Bureau and yielded results consistent with Passel’s estimates.

An estimated 11.8 million unauthorized immigrants were living in the United States in January 2007 compared to 8.5 million in 2000 (Hoefer, Rytina, and Campbell, 2006). Between 2000 and 2007, the unauthorized population increased 3.3 million; the annual average increase during this period was 470,000. Nearly 4.2 million (35 percent) of the total 11.8 million unauthorized residents in 2007 had entered in 2000 or later. An estimated 7.0 million (59 percent) were from Mexico. 17

The OIS reported an estimated 11.6 million unauthorized alien residents as of January 2008. This estimate marked the first decrease since the OIS began producing annual estimates in 2005. “The decrease in the size of the unauthorized population between 2007 and 2008,” the OIS demographers pointed out, “may be due to sampling error in the estimate of the foreign-born population in the 2007 ACS.” They estimated that the unauthorized alien population in the United States increased by 37% over the past eight years.18

Drawing on a different release of the CPS and a slightly different methodology, Steven Camarota and Karen Jensenius of the Center for Immigration Studies estimated that the unauthorized resident alien population fell to 10.8 million in February 2009. They used tabulations from the monthly CPS data rather than the March supplement to calculate a decrease of 1.7 million (13.7%) in 2009 from their high of 12.5 million unauthorized resident aliens in 2007. Despite the differences in methodology and data, these conclusions were comparable to Hoefer, Rytina, and Baker and to Passel and Cohn.19

By 2010, the estimates showed a continued decline in the number of the unauthorized alien residents. Both the CPS and the ACS data indicated that the estimated number dropped in 2008 and in 2009 before leveling off in 2010. According to Passel and Cohn, “The decline in the population of unauthorized immigrants from its peak in 2007 appears due mainly to a decrease in the number from Mexico, which went down to 6.5 million in 2010 from 7 million in 2007.”20

Analysis from the March Current Population Survey

The annual March CPS provides detailed socioeconomic data that are not available in the monthly CPS, shedding further light on the traits and trends in authorized migration. As Figure 2 illustrates, the 2010 distribution of the unauthorized population by region of origin was similar to Woodrow and Passel’s analysis of the 1986 data, despite the growth in overall numbers from 3.2 million in 1986 to 11.2 million in 2010. In 1986, 69% of the unauthorized aliens residing in the United States were estimated to be from Mexico, compared with 57% in 2010. There were 2.6 million, or 22%, from other Latin American countries in 2010. Asia’s share of the unauthorized alien residents appeared to have grown over this period (from 6% to 12%).21

As Figure 3 depicts, the portion of the resident unauthorized population that arrived since 2005 was estimated to be 9%, the lowest five-year interval since 1980-1984 (8%). An estimated 6.1 million (57%) of the unauthorized resident alien population came to the United States during the decade 1995-2004. According to Passel and Cohn, the inflow of unauthorized aliens between 1995 and 2004 exceeded the number of legal permanent residents (LPRs) who entered the country during that same period. The largest five-year interval was 2000-2004, during which an estimated 3.2 million unauthorized alien residents came to the United States. Reportedly, an estimated 150,000 unauthorized aliens from Mexico arrived annually during the period from 2007 to 2009, a level 70% below the estimated annual average of 500,000 during the first half of the decade.22

Passel and Cohn’s analysis of the 2010 CPS finds that about one-third of the estimated 11.2 million unauthorized aliens resided in two states: California and Texas, as the map reproduced in Figure 4 shows. Another group of states—Florida, New York, New Jersey and Illinois—have unauthorized resident alien populations exceeding half a million. Passel and Cohn also observed declines in the number of unauthorized resident aliens.

The four individual states where the number of unauthorized immigrants declined from March 2007 to March 2010 were New York, Florida, Virginia and Colorado. Additionally, the combined unauthorized immigrant population in Arizona, Nevada and Utah also decreased during that period, although the change was not statistically significant for any of those states individually.23
They also found that the combined unauthorized resident alien population of Arizona, Nevada, and Utah decreased from an estimated 850,000 in 2007 to an estimated 700,000 in 2010.24

As part of an earlier analysis, Passel and Cohn also calculated estimates of the number of households with unauthorized aliens. They reported that the number of persons living in families in which the head of the household or the spouse was an unauthorized alien was an estimated 16.6

million in 2008. They also reported that there were an estimated 1.5 million unauthorized children and an estimated 4.0 million citizen children who were living in families in which the head of the family or a spouse was unauthorized in 2008.25

Analysis from the American Community Survey

The American Community Survey (ACS) is a national sample survey that consists of non- overlapping samples from which the U.S. Census Bureau collects monthly household data over the course of a year. It was tested in 2000 and fully implemented in 2005.26 Although it does not enable the post-1986 times series analysis that the CPS offers, it has a larger sample size. As a result, OIS demographers Hoefer, Rytina, and Baker decided: “The ACS was selected for the estimates because of its large sample size, about 3 million households in 2007 compared to 100,000 for the March 2008 Current Population Survey, the primary alternative source of national data on the foreign-born population.” 27 They drew on the larger sample size of the ACS to analyze changes in the unauthorized resident alien population between 2000 and 2010.

Hoefer, Rytina, and Baker reported that the state of California had more unauthorized residents than any other state—an estimated 2.57 million unauthorized aliens in 2010.

As Figure 5 depicts, Texas followed with 1.77 million, and Florida had 760,000. However, California’s share of the total unauthorized population declined from 30% in 2000 to 24% in 2010, according to the OIS demographers.

Among the 10 leading states of residence of the unauthorized population in 2010, OIS reported that those with the largest average annual increases since 2000 were Texas, Arizona, and Georgia. Among the top 10 states, Georgia and Nevada had the greatest percentage increases in unauthorized aliens from 2000 to 2010.28

As Figure 6 illustrates, Mexico continued to dominate the unauthorized alien population in the ACS as it had in the CPS data shown in Figure 2.

The OIS demographers estimated that the unauthorized resident alien population from Mexico increased from 4.7 million in 2000 to 6.6 million in 2010, an estimate comparable to Passel and Cohn’s estimates of the source regions of the world depicted above in Figure 2. The 10 leading countries of origin represented over 80% of the unauthorized alien population in 2010 and are presented in Figure 6.

The other top source countries were El Salvador, Guatemala, Honduras, the Philippines, India, Ecuador, Brazil, Korea, and China.29

Although the stereotypic image of the unauthorized alien is often a young male, females have made up a sizeable minority of the unauthorized alien population for many years. 30 The OIS demographers estimated over 4.6 million females among the unauthorized alien population in 2010.

Males comprised the majority—an estimated 6.2 million or 57%—of the unauthorized alien population in 2010.

Most notably, males accounted for 62% of those in the 18 to 34 age group, and females accounted for 53% of the 45 and older age groups (590,000 in the 45 to 54 and 200,000 in the 55 and older ages groups).

As Figure 7 illustrates, unauthorized resident males tended to cluster in the peak working age groups of 18-24, 25-34, and 35-44. Although not larger in actual numbers, unauthorized resident females are more likely than males to be among those 17 and younger as well as those age 45 and older, according to the OIS demographers. 31

Analysis of the Monthly Current Population Survey

Steven Camarota and Karen Jensenius of the Center for Immigration Studies used the monthly CPS data to estimate that the unauthorized resident alien population has fallen from 12.5 million in 2007 to 10.8 million in 2009. Their analysis of the monthly data from January 2000 through January 2009 found that their estimate of the unauthorized alien population generally tends to be larger in the spring and summer, when employment in agriculture, hospitality, and construction tends to rise, although this pattern was not evidenced every year. 32

The monthly CPS provides more timely data, but offers much more limited demographic, immigration, and citizen information than the annual March CPS Supplement or the annual ACS. In the absence of more detailed immigration data, Camarota and Jensenius opted to use Hispanics aged 18 to 40 who have no more than a high school diploma for what they call “likely illegal population” or their proxy for unauthorized migration.33 They then offered the following observation:

[S]ince the peak in July 2007, the likely illegal Mexican population has declined 13.4 percent through February of this year…. On average, since January of 2008 the likely illegal population is about 7 percent lower each month compared to same month in the prior year. This is true through the first quarter of 2009. As already discussed, if we compare the two- year period of the first quarter of 2007 (which is reported as February) to the first quarter of 2009 we find a total decline of 10.9 percent in the likely illegal population.34

They posited that “the observed decline must be due to a combination of less-educated young Hispanic immigrants leaving the country and fewer entering the country.” Acknowledging that their analysis was over simplified and not inclusive of other factors likely to reduce unauthorized migration, Camarota and Jensenius estimated that out-migration of those Mexicans aged 18-40 who have no more than a high school diploma might have been more than twice as large in the 2006 to 2009 period as in the 2002 to 2005 period.35 After the more detailed ACS and the March CPS for 2009 are released, researchers are likely to explore whether similar in- and out-migration patterns are borne out in further analyses.

Contributing Factors

The research points to various factors that have contributed to the increase in unauthorized resident aliens over the past two decades as well as a leveling off of these trends. Historically, unauthorized migration is generally 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.36 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 maintain that lax enforcement of employer sanctions for hiring unauthorized aliens facilitated the “pull” for many years and that the ratcheting up of work site enforcement in 2007 and 2008 has subsequently mitigated the flow.37 Trend data suggest a correlation, but it remains difficult to demonstrate this element empirically, especially because the increased worksite enforcement and removals were coincident with the housing downturn and the onset of the economic recession.38
Political instability or civil unrest at home is another element that traditionally has induced people to risk unauthorized migration.39 Asylum seekers who enter the United States illegally have always been included in the estimates of the unauthorized alien population. Asylum claims ebbed and flowed in the 1980s and peaked in FY1996. Since FY1997, defensive asylum claims dropped by 53% by FY2009. Comparatively, asylum seekers have become a smaller share of the unauthorized resident alien population and do not account for the overall trends in the unauthorized resident aliens in recent years. 40

Although most policy makers have assumed that tighter border enforcement reduces unauthorized migration, some researchers have observed that the strengthening of the immigration enforcement provisions, most notably by the enactment of the Illegal Immigration Reform and Immigrant Responsibility Act of 1996 (IIRIRA), may have inadvertently increased the population of unauthorized resident aliens. This interpretation, generally referred to as a caging effect, argues that IIRIRA’s increased penalties for illegal entry, coupled with increased resources for border enforcement particularly after the September 11, 2001, terrorist attacks, stymied what had been a rather fluid movement of migratory workers along the southern border; this in turn raised the stakes in crossing the border illegally and created an incentive for those who succeed in entering the United States to stay.41

The current system of legal immigration is frequently cited as another factor contributing to the growth in unauthorized alien residents.42 There are statutory ceilings that limit the type and number of immigrant visas issued each year, which lead to wait-times for visas to become available to legally come to the United States. 43 Some observe that family members sometimes risk staying in the United States on an expired temporary visa or entering the United States illegally to be with their family while they wait for the visas to become available. It remains difficult, however, to demonstrate a causal link or to guarantee that increased levels of legal migration would absorb the current flow of unauthorized migrants.44 The increase in the number of aliens deported from the United States annually from 189,026 in 2001 to 387,242 in 2010 might also have had a chilling effect on family members weighing illegal presence.45

Some observers point to more elusive factors—such as shifts in immigration enforcement priorities away from illegal entry to removing suspected terrorists and criminal aliens, or discussions of possible “amnesty” legislation—when they assess the increase in unauthorized resident aliens from 2000 to 2007. It is difficult to measure whether, or to what extent, these other phenomena have contributed to the flow of unauthorized resident aliens.

Author:
Ruth Ellen Wasem, Specialist in Immigration Policy [email protected], 7-7342

Source:
This article, Unauthorized Aliens Residing in the United States: Estimates Since 1986, was published by the Congressional Research Service, September 22, 2011

Notes:
1 CRS analysis of the Current Population Survey for March 2008 found 37.2 million foreign-born residents in 2008. CRS Report RL33809, Noncitizen Eligibility for Federal Public Assistance: Policy Overview and Trends, by Ruth Ellen Wasem. In analysis discussed more fully below, demographer Jeffrey Passel of the Pew Hispanic Center made adjustments in this total to compensate for undercounting certain populations and estimated the total foreign-born population to be over 39 million. Jeffrey S. Passel and D’Vera Cohn, Trends in Unauthorized Immigration: Undocumented Inflow Now Trails Legal Inflow, Pew Hispanic Center, October 2, 2008.
2 The United States typically admitted or adjusted 600,000 to 1 million aliens annually, giving them the status of “legal permanent resident” (LPR), a term synonymous with the term immigrant. In addition to those foreign nationals who permanently reside legally in the United States, millions each year come temporarily on nonimmigrant visas, and some of these nonimmigrants (e.g., foreign students and intra-company business transfers) may reside legally in the United States for several years. It is also estimated that each year hundreds of thousands of foreign nationals overstay their nonimmigrant visas.
3 See CRS Report RS22446, Nonimmigrant Overstays: Brief Synthesis of the Issue, by Ruth Ellen Wasem.
4 8 U.S.C. § 1255a.
5 8 U.S.C. § 1160.
6 For a discussion of these recommendations, see National Commission on Terrorist Attacks Upon the United States, The 9/11 Commission Report, chap. 12.4, pp. 383-391, July 2004.
7 The U.S. Bureau of the Census conducts the CPS each month to collect labor force data about the civilian noninstitutionalized population. The March Supplement of the CPS gathers additional data about income, education, household characteristics, and geographic mobility for a larger sample—about 80,000 households. The CPS began collecting immigration data on the foreign born in 1994, and the first years were plagued by problems of weighting, particularly with the Asian population in the sample, and by over-reporting of naturalization by the foreign born. Most of these problems appear to have been resolved by 1996. For more information about the CPS, go to http://www.census.gov/cps/.
8 The American Community Survey (ACS) is a national sample survey that consists of non-overlapping samples from which the U.S. Census Bureau collects monthly household data over the course of a year. The Census Bureau fielded it along side the decennial census in 2000 and fully implemented it in 2005. For more information about the ACS, go to http://www.census.gov/acs/www/.
9 The demographers who conducted these analyses used some variant of a residual methodology to estimate the population (i.e., the estimated population remaining after citizens and authorized aliens are accounted for), another reason they were selected for this comparison. Demographers at the U.S. Census Bureau also have used a similar methodology to estimate the residual foreign born population in the 2000 decennial census, and they reported the following: “According to our calculations, the estimated residual foreign-born population counted in the 2000 census was 8,705,419. Assuming a 15-percent undercount rate yields a population of 10,241,669 in 2000.” They point out that the category of residual foreign born includes “quasi legal aliens” (i.e., aliens without legal status who have petitions pending or court cases underway that potentially would give them LPR status), as well as unauthorized aliens, and thus should not be considered an official estimate of unauthorized resident aliens. U.S. Census Bureau, Population Division Working Paper 61, Evaluating Components of International Migration: The Residual Foreign Born, by Joseph M. Costanzo, Cynthia Davis, Caribert Irazi, Daniel Goodkind, and Roberto Ramirez (June 2002).
10 Karen Woodrow and Jeffrey Passel, “Post-IRCA Undocumented Immigration to the United States: An Analysis Based on the June 1988 CPS,” in Undocumented Migration to the United States, by Frank D. Bean, Barry Edmonston, and Jeffrey Passel (RAND Corporation, 1990).
11 Annual Estimates of the Unauthorized Immigrant Population Residing in the United States and Components of Change: 1987 to 1997, by Robert Warren, Office of Policy and Planning, U.S. Immigration and Naturalization Service, September 2000.
12 U.S. Congress, House Committee on the Judiciary, Subcommittee on Immigration and Claims, Hearing on the U.S. Population and Immigration, August 2, 2001.
13 U.S. Immigration and Naturalization Service, Estimates of the Unauthorized Immigrant Population Residing in the United States, 1990 to 2000, January 31, 2003.
14 The Urban Institute, Undocumented Immigrants: Facts and Figures, by Jeffrey Passel, Randy Capps, and Michael Fix, January 12, 2004.
15 Jeffrey S. Passel and D’Vera Cohn, Trends in Unauthorized Immigration: Undocumented Inflow Now Trails Legal Inflow, Pew Hispanic Center, October 2, 2008.
16 Jeffrey S. Passel, “Unauthorized Migrants in the United States: Estimates, Methods, and Characteristics”, OECD Social, Employment and Migration Working Papers, No. 57, OECD Publishing, 2007.
17 Michael Hoefer, Nancy Rytina, and Bryan C. Baker, Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2007, Department of Homeland Security, Office of Immigration Statistics, 2008.
18 Michael Hoefer, Nancy Rytina, and Bryan C. Baker , Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2008, Department of Homeland Security, Office of Immigration Statistics, 2009.
19 Steven Camarota and Karen Jensenius, A Shifting Tide: Recent Trends in the Illegal Immigrant Population, Center for Immigration Studies, July 2009.
20 Jeffrey S. Passel and D’Vera Cohn, Unauthorized Immigrant Population: National and State Trends, 2010, Pew Hispanic Center, February 1, 2011.
21 Ibid.
22 Ibid. For analysis of LPR admissions, see CRS Report RL32235, U.S. Immigration Policy on Permanent Admissions, by Ruth Ellen Wasem.
23 Jeffrey S. Passel and D’Vera Cohn, Unauthorized Immigrant Population: National and State Trends, 2010, Pew Hispanic Center, February 1, 2011.
24 Ibid.
25 Jeffrey S. Passel and D’Vera Cohn, A Portrait of Unauthorized Immigrants in the United States, Pew Hispanic Center, April 14, 2009. For further analysis and a discussion of selected policy implications of mixed immigration status families, see CRS Report RL34500, Unauthorized Aliens’ Access to Federal Benefits: Policy and Issues, by Ruth Ellen Wasem.
26 Development of the ACS began in 1994, and the Census Bureau fielded it along side the decennial census in 2000.
27 Michael Hoefer, Nancy Rytina, and Bryan C. Baker , Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2010, Department of Homeland Security, Office of Immigration Statistics, 2011.
28 Ibid.
29 Ibid.
30 Comparatively, the gender split on the aliens who legalized through §245A of IRCA was 56% male and 44% female. Shirley J. Smith, Roger G. Kramer, and Audrey Singer, Characteristics and Labor Market Behavior of the Legalized Population Five Years Following Legalization, U.S. Department of Labor Division of Immigration Policy and Research, May 1996.
31 Michael Hoefer, Nancy Rytina, and Bryan C. Baker, Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2010, Department of Homeland Security, Office of Immigration Statistics, 2011.
32 The monthly CPS is based upon a sample of about 55,000 households compared to approximately 80,000 for the expanded March Supplement of the CPS. Camarota and Jensenius’ analysis is based upon a three-month moving average of the monthly CPS. Steven Camarota and Karen Jensenius, A Shifting Tide: Recent Trends in the Illegal Immigrant Population, Center for Immigration Studies, July 2009.
33 “We estimate that three-fourths of these young, less-educated, foreign-born Hispanic adults are illegal aliens and that roughly two-thirds of all adult illegal aliens are young, less-educated, Hispanic immigrants. This population can be seen as the likely illegal immigrant population.” Steven Camarota and Karen Jensenius, A Shifting Tide: Recent Trends in the Illegal Immigrant Population, Center for Immigration Studies, July 2009.
34 Steven Camarota and Karen Jensenius, A Shifting Tide: Recent Trends in the Illegal Immigrant Population, Center for Immigration Studies, July 2009.
35 Ibid.
36 For further analysis, see CRS Report RL32982, Immigration Issues in Trade Agreements, by Ruth Ellen Wasem.

37 CRS Report R40002, Immigration-Related Worksite Enforcement: Performance Measures, by Andorra Bruno.
38 Steven Camarota and Karen Jensenius, A Shifting Tide: Recent Trends in the Illegal Immigrant Population, Center for Immigration Studies, July 2009.
39 For a summary of this research, see Commission for the Study of International Migration and Cooperative Economic Development, Unauthorized Migration: An Economic Development Response, Appendix E, July 1990.
40 Not all humanitarian migrants are eligible for asylum or refugee status, and roughly 30% of all asylum cases in recent years have been approved. The legal definition of asylum in the INA is consistent with the refugee definition, which specifies that a refugee is a person who is unwilling or unable to return to his country of nationality or habitual residence because of a well-founded fear of persecution on account of race, religion, nationality, membership in a particular social group, or political opinion. CRS Report R41753, Asylum and “Credible Fear” Issues in U.S. Immigration Policy , by Ruth Ellen Wasem.
41 Wayne Cornelius, “Death at the Border: Efficacy and Unintended Consequences of U.S. Immigration Control Policy,” Population and Development Review, vol. 27, no.4 (December 2001); Wayne Cornelius, “Evaluating Recent US Immigration Control Policy: What Mexican Migrants Can Tell Us,” in Crossing and Controlling Borders: Immigration Policies and Their Impact on Migrants’ Journeys, ed. Mechthild Baumann, Astrid Lorenz, and Kerstin Rosenhow (Farmington, MI: Budrich Unipress Ltd, 2011); Thomas J. Espenshade, “Undocumented Migration to the United States: Evidence from a Repeated Trials Model,” in Undocumented Migration to the United States, by Frank D. Bean, Barry Edmonston, and Jeffrey Passel (RAND Corporation, 1990); Douglas S. Massey, Jorge Durand, and Nolan J. Malone, Beyond Smoke and Mirrors: Mexican Immigration in an Era of Economic Integration (Russell Sage Foundation, 2002).
42 U.S. Congress, Senate Committee on the Judiciary, Subcommittee on Immigration, Refugees and Border Security, Comprehensive Immigration Reform in 2009, Can We Do It and How? 111th Cong., 1st sess., April 30, 2009.
43 For analysis of immigration admissions, visa priority dates, and backlogs, see CRS Report RL32235, U.S. Immigration Policy on Permanent Admissions, by Ruth Ellen Wasem.
44 U.S. Congress, Senate Committee on the Judiciary, Subcommittee on Immigration, Refugees and Border Security, Comprehensive Immigration Reform in 2009, Can We Do It and How? 111th Cong., 1st sess., April 30, 2009.
45 Department of Homeland Security, Office of Immigration Statistics, Immigration Enforcement Actions: 2010, June 2011, http://www.dhs.gov/xlibrary/assets/statistics/publications/enforcement-ar-2010.pdf.