Unauthorized Aliens Residing in the United
States: Estimates Since 1986
Ruth Ellen Wasem
Specialist in Immigration Policy
August 25, 2009
Congressional Research Service
7-5700
www.crs.gov
RL33874
CRS Report for Congress
P
repared for Members and Committees of Congress
Unauthorized Aliens Residing in the United States: Estimates Since 1986
Summary
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 11.9 million in 2008. 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. Steven Camarota and Karen Jensenius of the Center
for Immigration Studies use the monthly version of the CPS to estimate that the unauthorized
resident alien population has fallen to 10.8 million in 2009. The estimates of unauthorized aliens
peaked at an estimated 12.4-12.5 million in 2007. About 44% of unauthorized alien residents in
2008 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 11.6 million unauthorized alien residents as of January 2008, up from 8.5 million in
January 2000. The OIS estimated that 61% of unauthorized alien residents were from Mexico, a
percentage comparable to Passel and D’Vera Cohn’s calculation of 59% from Mexico. 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.
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. Some observers maintain that lax enforcement of employer sanctions for hiring
unauthorized aliens had facilitated this “push-pull,” but it is difficult to demonstrate these
elements empirically.
Some researchers also suggest that the increased size of the unauthorized resident population
during the past decade 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. They also cite the backlog in processing immigrant petitions, which some argue
lead aliens to risk residing without legal status with their family in the United States while they
wait for the visas to become available.
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. Unauthorized aliens, they maintain, have been filling gaps in the U.S. labor market that
could be met by new categories of temporary foreign workers or legal immigrants. 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.
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.
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Unauthorized Aliens Residing in the United States: Estimates Since 1986
Contents
Background ................................................................................................................................ 1
Estimates Since 1986 .................................................................................................................. 2
Analysis from the March Current Population Survey ................................................................... 4
Analysis from the American Community Survey ......................................................................... 8
Analysis of the Monthly Current Population Survey .................................................................. 11
Contributing Factors ................................................................................................................. 12
Figures
Figure 1. Estimated Number of Unauthorized Resident Aliens, 1986-2009 .................................. 3
Figure 2. Unauthorized Resident Alien Population, by Place of Origin, 1986 and 2008 ................ 5
Figure 3. Unauthorized Resident Aliens in 2008, by Reported Year of Arrival.............................. 6
Figure 4. Unauthorized Resident Alien Population, by State ........................................................ 7
Figure 5. Top 10 States with Unauthorized Resident Aliens ......................................................... 8
Figure 6. Top 10 Source Countries of Unauthorized Resident Aliens............................................ 9
Figure 7. Age Distribution of Unauthorized Resident Aliens in 2008, by Gender ....................... 10
Contacts
Author Contact Information ...................................................................................................... 13
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Unauthorized Aliens Residing in the United States: Estimates Since 1986
Background
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
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.
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Unauthorized Aliens Residing in the United States: Estimates Since 1986
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
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).
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Unauthorized Aliens Residing in the United States: Estimates Since 1986
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
Figure 1. Estimated Number of Unauthorized Resident Aliens, 1986-2009
Millions
14
12.5
11.9
12
11.6 12.4
11.1
11.8
11.6
10.8
10.3
10
9.8
10.5
9.4
9.3
8.4
8
7.0
5.8
6
5.0
4
3.5
3.2
3.4
1.9
2
0
1986 1988 1990 1992
1996
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
Woodrow & Passel
Warren
revised Warren
Hoefer, Rytina & Baker
Passel & Cohn
Passel, Capps & Fix
Camarota & Jensenius
Sources: CRS presentation of analyses of U.S. Census and CPS data conducted by Karen Woodrow and Jeffrey
Passel (1986 and 1990); Robert Warren (1996, 2000, and 2003); Jeffrey Passel, Randy Capps, and Michael Fix
(2002); Passel and D’Vera Cohn (2008); Michael Hoefer, Nancy Rytina, and Bryan Baker (2009); and Steven
Camarota and Karen Jensenius (2009).
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
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.
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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
More recently, Michael Hoefer, Nancy Rytina, and Bryan C. Baker of the Department of
Homeland Security’s (DHS’s) Office of Immigration Statistics (OIS) published their 2008
estimates of the unauthorized resident alien population and yielded results consistent with
Passel’s estimates discussed above. OIS demographers Hoefer, Rytina, and Baker drew their
estimates from the American Community Survey (ACS) of the U.S. Census Bureau. The OIS
reported an estimated 11.6 million unauthorized alien residents as of January 2008, up from 8.5
million in January 2000. This estimate, however, was down from their high of 11.8 million in
2007 and 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.”16 They estimated that the unauthorized alien population in the
United States increased by 37% over the past eight years.17
Using the monthly CPS data, Steven Camarota and Karen Jensenius of the Center for
Immigration Studies estimated that the unauthorized resident alien population has fallen to 10.8
million in February 2009, as Figure 1 depicts. They reported a decrease of 1.7 million (13.7%)
from their high of 12.5 million unauthorized resident aliens in 2007.18
Analysis from the March Current Population Survey
The annual March CPS provides detailed socioeconomic data that are not available in the
monthly CPS, and the most commonly cited published estimate—that 11.9 million unauthorized
aliens were residing in the United States—is based on the CPS of March 2008. According to this
analysis by Passel and his co-author D’Vera Cohn, Mexicans made up more than half of
undocumented immigrants—59% of the total, or about 7.0 million. They estimated that 2.6
million (22%) were from other Latin American countries. About 11% were from Asia, 4% from
Europe and Canada, and 4% from the rest of the world.19
As Figure 2 illustrates, the 2008 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 11.9 million in 2008. In 1986, 69% of the unauthorized
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 Department of Homeland Security, Office of Immigration Statistics, Estimates of the Unauthorized Immigrant
Population Residing in the United States: January 2008, by Michael Hoefer, Nancy Rytina, and Bryan C. Baker, 2009.
17 Department of Homeland Security, Office of Immigration Statistics, Estimates of the Unauthorized Immigrant
Population Residing in the United States: January 2008, by Michael Hoefer, Nancy Rytina, and Bryan C. Baker, 2009.
18 Steven Camarota and Karen Jensenius, A Shifting Tide: Recent Trends in the Illegal Immigrant Population, Center
for Immigration Studies, July 2009.
19 Jeffrey S. Passel and D'Vera Cohn, A Portrait of Unauthorized Immigrants in the United States, Pew Hispanic
Center, April 14, 2009.
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aliens residing in the United States were estimated to be from Mexico, compared with 59% in
2008. Asia’s share of the unauthorized alien residents appeared to have grown over this period
(from 6% to 11%), as did the portion from the “other” parts of the world. Note that Canada is
grouped with North and South America (excluding Mexico) in 1986 and with Europe in 2008.20
Figure 2. Unauthorized Resident Alien Population, by Place of Origin, 1986 and 2008
1986
2008
Mexico
59%
Mexico
69%
Other
Asia
4%
6%
Europe
Asia
2%
11%
North & South America
23%
Europe &
Canada
4%
Other Latin America
22%
3.2 million
11.9 million
Source: CRS presentation of analysis of Current Population Survey data conducted by Karen Woodrow and
Jeffrey Passel (1990), and Jeffrey Passel and D’Vera Cohn (2009).
Note: Canada is grouped with North and South America (excluding Mexico) in 1986 and with Europe in 2008.
As Figure 3 depicts, an estimated 6.8 million (56.6%) of the unauthorized resident alien
population came to the United States during the decade 1995-2004. According to Passel, the
inflow of unauthorized aliens between 1998 and 2004 exceeded the number of legal permanent
residents (LPRs) who entered the country during that same period. Passel projected that
unauthorized aliens accounted for about 5.4% of the civilian labor force in March 2008, or about
8.3 million workers out of a labor force of 154 million.21
20 Ibid.
21 Ibid. For analysis of LPR admissions, see CRS Report RL32235, U.S. Immigration Policy on Permanent Admissions,
by Ruth Ellen Wasem.
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Figure 3. Unauthorized Resident Aliens in 2008, by Reported Year of Arrival
2000-2004
30.8%
1995-1999
25.8%
3.7 million
3.1 million
1.6 million
2.0 million
2005-2008
13.3%
1.6 million
1990-1994
16.7%
pre-1990
13.3%
Source: CRS presentation by analysis of Current Population Survey data conducted by Jeffrey Passel & D’Vera
Cohn (2009).
Passel’s analysis of the 2008 CPS finds that about half of the estimated 11.9 million unauthorized
aliens resided in four states: California, Texas, Florida, and New York. These four states had
unauthorized resident alien populations ranging from about 900,000 to 2.7 million, as the map
reproduced in Figure 4 shows. In another group of four states—New Jersey, Arizona, Georgia,
and Illinois—the estimated number of unauthorized aliens hovered around half a million. These
top eight states housed more than two-thirds of unauthorized resident aliens (68%). Passel also
found that there were 28 high-growth states scattered across the mid-Atlantic, Midwest,
Mountain, and Southeast regions. These 28 high-growth states had 32% of the unauthorized
resident alien population in 2008, more than double their 14% share in 1990.22
22 Jeffrey S. Passel and D'Vera Cohn, A Portrait of Unauthorized Immigrants in the United States, Pew Hispanic
Center, April 14, 2009.
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Unauthorized Aliens Residing in the United States: Estimates Since 1986
Figure 4. Unauthorized Resident Alien Population, by State
Estimates for 2008
Source: CRS presentation of analysis of Current Population Survey data conducted by Jeffrey Passel & D’Vera
Cohn (2009).
Notes: Passel and Cohn report that there were no states in 2008 with an estimated unauthorized alien
population between 575,000 and 900,000.
In addition to estimating the number of individuals who were unauthorized aliens, 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 2008.23
23 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.
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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 2005.24 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.” 25 They drew on the larger sample size of the ACS to
analyze changes in the unauthorized resident alien population between 2000 and 2008.
Figure 5. Top 10 States with Unauthorized Resident Aliens
Estimates for 2000 and 2008
2000
2008
2.51
California
2.85
1.09
Texas
1.68
0.80
Florida
0.84
0.54
New York
0.64
0.33
Arizona
0.56
0.44
Illinois
0.55
0.22
Georgia
0.46
0.35
New Jersey
0.40
0.26
North Carolina
0.38
0.17
Nevada
0.28
1.76
All other
2.95
Millions
Source: CRS presentation of American Community Survey data analyzed by Michael Hoefer, Nancy Rytina, and
Bryan Baker (2009).
24 Development of the ACS began in 1994, and the Census Bureau fielded it along side the decennial census in 2000.
25 Department of Homeland Security, Office of Immigration Statistics, Estimates of the Unauthorized Immigrant
Population Residing in the United States: January 2008, by Michael Hoefer, Nancy Rytina, and Bryan C. Baker, 2009.
For alternative analyses, see Jeffrey S. Passel and D'Vera Cohn, A Portrait of Unauthorized Immigrants in the United
States, Pew Hispanic Center, April 14, 2009.
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Hoefer, Rytina, and Baker reported that the state of California had more unauthorized residents
than any other state—an estimated 2.85 million unauthorized aliens in 2008. As Figure 5 depicts,
Texas followed with 1.68 million, and Florida had 840,000. However, California’s share of the
total unauthorized population declined from 30% in 2000 to 25% in 2008, according to the OIS
demographers. Among the 10 leading states of residence of the unauthorized population in 2008,
OIS reported that those with the largest average annual increases since 2000 were Texas (70,000),
California (40,000), Arizona (30,000), and Georgia (30,000). The top 10 states with the greatest
percentage increases in unauthorized aliens from 2000 to 2008 were Georgia (105%) and Nevada
(70%).26 These findings were consistent with Passel and Cohn, as previously discussed.
Figure 6. Top 10 Source Countries of Unauthorized Resident Aliens
Estimates for 2000 and 2008
2000
2008
4.68
Mexico
7.03
0.43
El Salvador
0.57
0.29
Guatemala
0.43
0.20
Philippines
0.30
0.16
Honduras
0.30
0.18
Korea
0.24
0.19
China
0.22
0.10
Brazil
0.18
0.11
Ecuador
0.17
0.12
India
0.16
2.00
All other
2.00
Millions
Source: CRS presentation of American Community Survey data analyzed by Michael Hoefer, Nancy Rytina, and
Bryan Baker (2009).
As Figure 6 illustrates, Mexico continued to dominate the unauthorized alien population. The
OIS demographers estimated unauthorized immigrant population from Mexico increased from 4.7
million in 2000 to 7.0 million in 2008 (61%), an estimate comparable to Passel’s estimates of the
source regions of the world depicted above in Figure 2. The 10 leading countries of origin
represented 83% of the unauthorized alien population in 2008 and are presented in Figure 6. The
26 Department of Homeland Security, Office of Immigration Statistics, Estimates of the Unauthorized Immigrant
Population Residing in the United States: January 2008, by Michael Hoefer, Nancy Rytina, and Bryan C. Baker, 2009.
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other top source countries were El Salvador, Guatemala, the Philippines, Honduras, Korea, China,
Brazil, Ecuador, and India. The greatest percentage increases during the period 2000-2008 among
the top 10 countries were among unauthorized aliens from Honduras (81%), Brazil (72%), the
Philippines (51.%), Ecuador (50%), and Guatemala (48%). Bear in mind, however, that increases
of a few hundred thousand from countries other than Mexico may yield substantial percentage
increases that are otherwise small when contrasted to Mexican inflows. 27
Figure 7. Age Distribution of Unauthorized Resident Aliens in 2008, by Gender
Females
Males
17 and under
0.73
0.81
18 to 24
0.59
1.03
25 to 34
1.57
2.48
35 to 44
1.38
1.67
45 to 54
0.48
0.51
55 and over
0.19
0.16
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0.50
1.00
1.50 2.00
2.50
3.00
Millions
Source: CRS presentation of American Community Survey data analyzed by Michael Hoefer, Nancy Rytina, and
Bryan Baker (2009).
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. 28 The OIS
demographers estimated almost 5.0 million females among the unauthorized alien population in
27 Department of Homeland Security, Office of Immigration Statistics, Estimates of the Unauthorized Immigrant
Population Residing in the United States: January 2008, by Michael Hoefer, Nancy Rytina, and Bryan C. Baker, 2009.
28 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.
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2008. Males comprised the majority—an estimated 6.6 million or 57%—of the unauthorized alien
population in 2008. Most notably, males accounted for 62% of those in the 18 to 34 age group.
Females accounted for 52% of the 45 and older age 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.
Unauthorized resident females, on the other hand, appeared to be distributed more evenly across
age groups than males. 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. 29
Analysis of the Monthly Current Population Survey
As noted above in Figure 1, 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. 30
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.31 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.32
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
29 Department of Homeland Security, Office of Immigration Statistics, Estimates of the Unauthorized Immigrant
Population Residing in the United States: January 2008, by Michael Hoefer, Nancy Rytina, and Bryan C. Baker, 2009.
30 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.
31 “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.
32 Steven Camarota and Karen Jensenius, A Shifting Tide: Recent Trends in the Illegal Immigrant Population, Center
for Immigration Studies, July 2009.
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2006 to 2009 period as in the 2002 to 2005 period.33 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 and a possible 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.34 Accordingly, the current economic recession may have curbed the migration
of unauthorized aliens, particularly because sectors that traditionally rely on unauthorized aliens,
such as construction, services, and hospitality, are especially hard hit. Political instability or civil
unrest at home is another element that traditionally has induced people to risk unauthorized
migration, but the motives for such migrations are sometimes mixed with the economic hardships
that, in turn, are often correlated with political upheaval.35
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.36 Trend data suggest a correlation, but it
remains difficult to demonstrate this element empirically, especially because the increased
worksite enforcement was coincident with the housing downturn and the onset of the current
economic recession.37
Although most policy makers have assumed that tighter border enforcement would reduce
unauthorized migration, some researchers observe 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.38 This perspective 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.39
33 Ibid.
34 For further analysis, see CRS Report RL32982, Immigration Issues in Trade Agreements, by Ruth Ellen Wasem.
35 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.
36 CRS Report R40002, Immigration-Related Worksite Enforcement: Performance Measures, by Andorra Bruno.
37 Steven Camarota and Karen Jensenius, A Shifting Tide: Recent Trends in the Illegal Immigrant Population, Center
for Immigration Studies, July 2009.
38 For trends in apprehensions of unauthorized aliens, see CRS Report RL32562, Border Security: The Role of the
U.S. Border Patrol, by Chad C. Haddal.
39 For analysis of the IIRIRA’s effect on unauthorized alien residents, see 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). For an analysis of the reduction in unauthorized alien apprehensions after IRCA, see
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).
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The current system of legal immigration is frequently cited as another factor contributing to the
growth in unauthorized alien residents.40 There are statutory ceilings that limit the type and
number of immigrant visas issued each year, which lead to wait-times for immigrant petitions to
be processed and visas to become available to legally come to the United States. 41 According to
this interpretation, many foreign nationals who would otherwise prefer to come to the United
States legally resort to illegal avenues in frustration. This contributing factor also presupposes
that current legal immigration categories are out-dated and unresponsive to labor market needs.
Unauthorized aliens, they maintain, have been filling gaps in the U.S. labor market that could be
met by new categories of temporary foreign workers or legal immigrants. 42 Of the pending cases
awaiting an LPR visa, reportedly almost 2 million are family members of people legally in the
United States (i.e., U.S. citizens or LPRs). Many observe that these family members sometimes
risk residing without legal status with their family in the United States while they wait for the
petitions to be processed or 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.43
Some observers point to more elusive factors—such as shifts in immigration enforcement
priorities or discussions of possible “amnesty” legislation—when they assess the increase in
unauthorized resident aliens. It is difficult to measure whether, or to what extent, these other
phenomena have contributed to the flow of unauthorized resident aliens.
Author Contact Information
Ruth Ellen Wasem
Specialist in Immigration Policy
rwasem@crs.loc.gov, 7-7342
40 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.
41 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.
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 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.
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