U.S. Census Bureau

Evaluating Components of International Migration:
The Residual Foreign Born

Joe Costanzo
Cynthia Davis
Caribert Irazi
Daniel Goodkind
Roberto Ramirez

DAPE Task Team #5 - Unauthorized Migration Evaluation Team (UMET)

Population Division
U. S. Bureau of the Census
Washington, D.C. 20233

December 2001

Working Paper Series No. 61

DISCLAIMER:

This paper reflects the results of research undertaken by the authors. It has undergone a more limited review than official Census Bureau publications. This paper is not meant to represent the official view of the U.S. Census Bureau. This paper has been prepared to inform interested parties of on-going research and to encourage discussion.


Synopsis

On March 1, 2001, the U.S. Census Bureau issued the recommendation of the Executive Steering Committee for A.C.E. Policy (ESCAP) that the Census 2000 Redistricting Data not be adjusted based on the Accuracy and Coverage Evaluation (A.C.E.). By mid-October 2001, the Census Bureau had to recommend whether Census 2000 data should be adjusted for future uses, such as the census long form data products, post-censal population estimates, and demographic survey controls. In order to inform that decision, the ESCAP requested that further research be conducted.

Between March and September 2001, the Demographic Analysis-Population Estimates (DAPE) research project addressed the discrepancy between the demographic analysis data and the A.C.E. adjusted estimates of the population. Specifically, the research examined the historical levels of the components of population change to address the possibility that the 1990 Demographic Analysis understated the national population and assessed whether demographic analysis had not captured the full population growth between 1990 and 2000. Assumptions regarding the components of international migration (specifically, emigration, temporary migration, legal migration, and unauthorized migration) contain the largest uncertainty in the demographic analysis estimates. Therefore, evaluating the components of international migration was a critical activity in the DAPE project.

This report focuses on the evaluation of the U.S. Census Bureau's estimated residual foreign-born population (including both unauthorized and quasi-legal migrants) in 1990 and 2000. The estimates shown here were calculated in conjunction with estimates of other components of international migration: legal permanent migration and legal temporary migration. These components of international migration, along with assumed deaths and emigrants, are subtracted from a total foreign-born population yielding a residual count.

This residual foreign-born population is not an estimate of the number of unauthorized migrants. This estimate also includes people who are here legally but are not yet included in the official estimates of legal migrants and refugees. It also includes people in "quasi-legal" status who are awaiting action on their legal migration requests. Because the estimate was derived from a residual methodology, any limitations in the methods or in the measurement of other migration components are reflected in the residual number. In addition, our assumptions include a great deal of uncertainty, especially for small migration components. Therefore, the residual may be quite different from the actual number of unauthorized migrants.

According to our calculations, the estimated residual foreign-born population was 3,765,906 in 1990 and 8,705,419 in 2000. The residual foreign born were less likely to be male (48.4 percent) in 1990 than in 2000 (54.2 percent). Of the residual foreign born, 26.8 percent were from Mexico in 1990 and 44.5 percent were from Mexico in 2000.


Outline Skip this navigation menu

Summary

Background

Methods

  1. Method 1: Woodrow's 1990 DA Estimates of the Residual Foreign-Born Population, 1990
  2. Method 2: Ahmed's Preliminary Estimates of the Residual Foreign-Born Counted in the 1990 Census
  3. Method 3 (1990): DAPE Estimates of the Residual Foreign-Born Population, 1990
  4. Method 3 (2000): DAPE Estimates of the Residual Foreign-Born Population, 2000

Limitations

Results

Next Steps

Appendix A. Tables*

This residual foreign-born population is not an estimate of the number of unauthorized migrants. This estimate also includes people who are here legally but are not yet included in the official estimates of legal migrants and refugees. It also includes people in "quasi-legal" status who are awaiting action on their legal migration requests. Because the estimate was derived from a residual methodology, any limitations in the methods or in the measurement of other migration components are reflected in the residual number. In addition, our assumptions include a great deal of uncertainty, especially for small migration components. Therefore, the residual may be quite different from the actual number of unauthorized migrants.

* Numbers shown in tables may differ from numbers produced in actual calculations due to rounding.

All Tables in one Excel file (67k) | All Tables in one PDF file [PDF 283k]
A-1. Estimates of Residual Foreign Born by DA Race, Sex, and Age: 1990 (Census Level) Excel (16k) | PDF (26k)
A-1a. Estimates of the Residual Foreign Born, adjusted for 15 percent undercount, by DA Race, Sex, and Age: 1990
A-1b. Estimates of the Residual Foreign Born, adjusted for 20 percent undercount, by DA Race, Sex, and Age: 1990
Excel (18k) | PDF (52k)
A-2. Estimates of the Residual Foreign Born by DA Race & Hispanic Origin, Sex, and Age: 1990 (Census Level) Excel (17k) | PDF (26k)
A-2a. Estimates of the Residual Foreign Born, adjusted for 15 percent undercount, by DA Race & Hispanic Origin, Sex, and Age: 1990
A-2b. Estimates of the Residual Foreign Born, adjusted for 20 percent undercount, by DA Race & Hispanic Origin, Sex, and Age: 1990
Excel (19k) | PDF (29k)
A-3. Estimates of the Residual Foreign Born by DA Race, Sex, and Age: 2000 (Census Level) Excel (16k) | PDF (26k)
A-3a. Estimates of the Residual Foreign Born, adjusted for 15 percent undercount, by DA Race, Sex, and Age: 2000
A-3b. Estimates of the Residual Foreign Born, adjusted for 20 percent undercount, by DA Race, Sex, and Age: 2000
Excel (18k) | PDF (26k)
A-4. Estimates of the Residual Foreign Born by DA Race & Hispanic Origin, Sex, and Age: 2000 (Census Level) Excel (17k) | PDF (27k)
A-4a. Estimates of the Residual Foreign Born, adjusted for 15 percent undercount, by DA Race & Hispanic Origin, Sex, and Age: 2000
A-4b. Estimates of the Residual Foreign Born, adjusted for 20 percent undercount, by DA Race & Hispanic Origin, Sex, and Age: 2000
Excel (19k) | PDF (29k)
A-5. Estimates of the Residual Foreign Born by Place of Birth and Sex, 1990 Excel (22k) | PDF (26k)
A-6. Estimates of the Residual Foreign Born by Place of Birth and Sex, 2000 Excel (22k) | PDF (27k)

Appendix B. Reference Materials: Bibliography

  1. Demographic Analysis-Population Estimates (DAPE) Research Project Reports Related to Evaluating Components of International Migration
  2. Census Bureau Technical Documentation Related to Estimating the Residual Foreign-Born Population
  3. Non-Census Bureau Documentation on Measuring the Residual Foreign-Born Population and Unauthorized Migration

Appendix C. Comparing Estimates of the Residual Foreign Born with Estimates others have made of the Unauthorized Migrant Population

Population Division Working Papers


Estimating the Residual Foreign-Born Population: 1990 and 2000

Summary

Estimates of the residual foreign-born population shown here were calculated in conjunction with estimates of other components of international migration: legal permanent migration and legal temporary migration. These "known" components of international migration, along with assumed deaths and emigrants, are subtracted from a total foreign-born population yielding a residual count. This residual foreign-born population is not an estimate of the number of unauthorized migrants. This estimate also includes people who are here legally but are not yet included in the official estimates of legal migrants and refugees. It also includes people in "quasi-legal" status who are awaiting action on their legal migration requests. Because the estimate was derived from a residual methodology, any limitations in the methods or in the measurement of other migration components are reflected in the residual number. In addition, our assumptions include a great deal of uncertainty, especially for small migration components. Therefore, the residual may be quite different from the actual number of unauthorized migrants.

According to our calculations, the estimated residual foreign-born population counted in the 1990 census was 3,765,906. Assuming a 15-percent undercount rate (discussed later in this report) yields a population of 4,430,478 in 1990.

Selected characteristics of the residual foreign-born population counted in Census 1990 include:

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.

Selected characteristics of the residual foreign-born population counted in Census 2000 include:

(See Tables in Appendix A for more details by age, sex, race, Hispanic origin, and place (country) of birth for both 1990 and 2000 estimates, but recall that these estimates are not of the unauthorized migrant population.)

The basic methodological approach for both 1990 and 2000 was the residual method. A decennial census sample file was used for the foreign-born population base as of April 1st. Estimates of legal permanent residents (LPRs), temporary migrants, and Special Agricultural Workers (SAWs) and Pre-1982 entrants into the U.S. (LAWs) were subtracted from the foreign-born population base.1 Assumptions were made about emigration and mortality of the legal and IRCA-legalized populations. Race and Hispanic origin distributions were assigned by age, sex, and place (country) of birth.2 Population undercount assumptions were not included in this methodology. However, estimates of the total residual foreign-born population are shown here at different assumed levels of undercoverage.


Background

Since the 1980s, empirically-based estimates have been developed to measure the population of persons illegally present in the United States. Prior to these studies, estimates of the unauthorized population ranged from one to twelve million.3

The most straightforward and simplest measure of the unauthorized population has been the residual method. This method essentially removes the legal component of the census or survey-based foreign-born population, leaving behind the unauthorized component as a residual. Estimates obtained using residual methods most often are derived from federal data providers: the U.S. Census Bureau and the Immigration and Naturalization Service (INS). Using more than one data source is required given that no one source of data includes all the necessary components for directly estimating the unauthorized population.

Adjustments to these estimates have been made since the early 1980s. Researchers have incorporated new components into their estimates of unauthorized migration. (Woodrow-Lafield, 1991; Ahmed, 1995; Passel & Clark, 1998; Bean et al., 2001) In an effort to improve the validity of the measures, we have adjusted characteristics of immigrants entering under the Special Agriculture Workers (SAWs) program, emigrants leaving the United States, and nonimmigrants (temporary admissions not for permanent residence).

Although the INS is the U.S. federal agency responsible for providing the official estimates of the unauthorized population, the U.S. Census Bureau must include assumptions about any migrants not counted in the official legal immigration data.

As part of the Bureau's evaluation of Census 2000 results and the determination as to whether the Census 2000 counts should be adjusted for purposes other than reapportionment and redistricting, the Population Division at the Census Bureau has reviewed the reliability of its demographic analysis and population estimates methodology, and the underlying components of population change, including components of international migration.

This report provides an evaluation of the residual foreign-born component of international migration as it relates to the U.S. resident population on April 1, 1990 and April 1, 2000. This residual foreign-born population is not an estimate of the number of unauthorized migrants. This estimate also includes people who are here legally but are not yet included in the official estimates of legal migrants and refugees. It also includes people in "quasi-legal" status who are awaiting action on their legal migration requests. Because the estimate was derived from a residual methodology, any limitations in the methods or in the measurement of other migration components are reflected in the residual number. In addition, our assumptions include a great deal of uncertainty, especially for small migration components. Therefore, the residual may be quite different from the actual number of unauthorized migrants.


Methods

In addition to detailing our own approach to estimating the residual foreign-born population (of which the unauthorized population is a part), this report highlights two other methods used at the Census Bureau during the 1990s to estimate the residual foreign-born population as of 1990.4

In order to answer the question placed before us, "Is the assumed flow of unauthorized migration realistic?", the Demographic Analysis-Population Estimates (DAPE) team reviewed the related research conducted in the late 1980s and in the 1990s at the Census Bureau as well as other studies addressing this issue. (See Appendix B for details.)

We identified two methods as having been used in the Bureau's estimation of the residual foreign-born population as of 1990. These methods will be referred to as: 1) Woodrow's 1990 DA estimates (1991); and 2) Ahmed's 1990 preliminary census estimates (1995).

Each of the methods relies on residual techniques common to the estimation of hard-to-count populations such as the unauthorized population. For a residual technique, one or more identifiable components are subtracted from a comprehensive universe (such as the decennial census' total foreign-born population) yielding a residual estimate of a population for which no direct measure exists.


Method 1: Woodrow's 1990 DA Estimates of the Residual Foreign-Born Population, 19905

Woodrow (1991) developed preliminary estimates of the 1990 residual foreign-born population as part of the 1990 Demographic Analysis Evaluation Project.6 This project was undertaken and completed prior to the internal release of 1990 census sample data, therefore, 1990 census data were not used in these calculations.

Woodrow estimates the residual foreign-born population residing in the United States on April 1, 1990 using two approaches yielding "direct" and "implicit" estimates, as termed by Woodrow. For the first approach, a residual method was applied to the 1989 Current Population Survey (CPS) to derive the size of the residual foreign-born population. This CPS-based estimate was then extended to reflect the size of the residual foreign-born population on April 1, 1990 by assuming a linear population growth rate. Because of the uncertainties associated with the sampling and non-sampling errors as well as census under-coverage, a range of possible estimates was derived. Finally, from the range of possible values, a (mid)point estimate was determined for six separate census undercount scenarios. The preferred undercount scenario of 25 percent yielded a midpoint estimate of 3.3 million unauthorized persons.7

For her second approach (yielding an "implicit" estimate) Woodrow carried forward the 1980 estimate of the residual foreign-born population and estimated change in the unauthorized and IRCA-legalized populations between 1980 and 1990 based on alternative post-1980 demographic assumptions from previous CPS-based estimates. This approach requires estimates of: 1) 1980 residual foreign-born population estimate; 2) the number of IRCA legalizations (LAWs and SAWs); and 3) the net change during the period.

Based on her analysis Woodrow determined likely ranges under each method, with a 1990 estimate of 3.3 million (total residual foreign-born population in the United States) falling in the middle of each range. When considering census undercoverage (20 to 30 percent, as estimated by Woodrow) and the effect of CPS sampling and estimation errors, the estimates range from a low of 1.9 million to a high of 4.5 million.

From her 1989 November CPS data carried forward to April 1, 1990, Woodrow estimated a residual foreign-born population of 2.1 million was counted in the 1990 census (with a range of 1.6 million to 2.7 million).

Some assumptions may widen the lower end of the ranges even further. For example, the residual method based on the 1989 CPS assumed that no SAWs were counted among the foreign born because the number of SAWs then known to be living in the U.S. could not be confirmed (1991, p. 16; p. 29). Yet, Woodrow cited 1.3 million SAW applications from June 1, 1987 to November 30, 1988. The inclusion of a portion of these SAWs would reduce the level of Woodrow's proposed range.

Woodrow assumed an annual net flow of about 200,000 residual foreign born during the 1980s.8 She based this figure on previous research using November 1979, April 1983, June 1986, June 1988, and November 1989 CPS data. With each new CPS supplement Woodrow supported the range of between 100,000 and 300,000 net annual growth in the residual foreign-born population.

In her 1991 report, Woodrow cautioned the interpretation and use of her preliminary estimates citing the following issues:

  1. Accuracy of the prior research (e.g., 2.1 million residual foreign-born persons counted in the 1980 census);
  2. Additional (and unaccounted for) categories of foreign born in the U.S.;
  3. Assumptions about the foreign-born undercount;
  4. Lack of availability (at the time of her research) of 1990 census data; and
  5. Definition and applicability of "usual place of residence" to this population


Method 2: Ahmed's Preliminary Estimates of the Residual Foreign Born Counted in the 1990 Census

Following the preliminary Woodrow report (1991), 1990 census results were used to improve residual techniques. In the early 1990s, Bureau work on unauthorized migration (Fernandez, E.W. and J.G. Robinson, 1994; Robinson, J.G., 1994) and emigration (Ahmed, B. and J.G. Robinson, 1994) led to the first extensive internal report regarding the residual equation and how components were derived to estimate an unauthorized population counted in the 1990 census.

Assuming no coverage or estimation error in the census or in the components, Ahmed (1995) estimated that 942,000 residual foreign born were counted in the 1990 census. This figure is well below the 3.3 million total residual foreign-born population put forward in Method 1 by Woodrow (1991), as well as Woodrow's estimated 2.1 million enumerated residual foreign-born population as of 1990.

The Ahmed method uses residual techniques based on the 1990 decennial census, INS data on legal admissions and IRCA legalizations, and components of change. The 1990 census data represent the counted foreign-born population as of April 1, 1990, whereas the other components yield the expected legal population at the census date. These include the number of legal immigrants and refugees (and deaths to and emigration of these populations), foreign students, and persons illegally present who legalized under IRCA.9 This technique assumes that the difference between the census-based total foreign-born estimate and the legal population will reflect the residual foreign-born population as counted in the 1990 census.

In his estimates, Ahmed restricts his population to those who entered between 1980 and 1990. This has an effect on both the legal and IRCA-legalized population estimates used in his method.

The legal population (on the INS legal admissions files) consists of both new arrivals and adjustees. The new arrivals' year of entry is assumed to be that of the INS file; in other words, those new arrivals included in the 1980 INS file are assumed to have entered the U.S. in 1980. Adjustees were present in the U.S. prior to admission to permanent legal status, and have years of entry earlier than the year in which they appear on the INS files. Ahmed does not take this into account, but assumes that the new arrivals and the adjustees have years of entry corresponding the INS file year.

The IRCA-legalized population who entered the U.S. prior to 1980 was also excluded from his method.10 He states an assumption that anyone who had come before 1980 would have been legalized under IRCA. However, the LAW population (pre-1982 entrants) would for the most part have entered the U.S. prior to 1980 (given the pre-1982 requirements as set in the IRCA legislation), and would be excluded from the 1980-1990 restricted universe in Ahmed's work. Had Ahmed included this population, his estimates of the residual foreign-born population would have been even lower, as this IRCA-legalized component is part of the legal population subtracted from the total foreign-born population counted in the census.

For a comparable universe, the legal immigrant population (in the INS Legal Permanent Resident files) should have been restricted to the legal immigrant population with years of entry 1980 to 1990. By including the additional persons (who adjusted from a nonimmigrant status, but who arrived prior to 1980) in the legal population yields a significantly decreased residual foreign-born population count.

In his calculations of legal immigration from the INS legal admissions files, Ahmed appears to have included an additional quarter of admissions (adding January through March 1980). The addition of this extra quarter incorrectly overestimates the legal population.

Unlike the DAPE Method (discussed below), Ahmed does not apply emigration and death rates to the IRCA-legalized population as he does with the legal population. Fortunately, Ahmed does age the IRCA-legalized population an average of two years (from an averaged application year of 1988) to April 1990.

Ahmed restricted the temporary migrant population to the foreign student population for his work. Had this population been more broadly defined (to include other temporary residents such as H-1B workers) the overall residual foreign-born population estimate would have been lower.

The Ahmed estimates were never incorporated into any official estimates produced by the Census Bureau.


Method 3 (1990): DAPE Estimates of the Residual Foreign-Born Population, 1990

The 1990 residual foreign-born estimate was calculated in conjunction with estimates of other components of international migration: legal permanent migration and legal temporary migration. These "known" components of international migration, along with assumed deaths and emigrants, are subtracted from a total foreign-born population yielding a residual count. This residual foreign-born population is not an estimate of the number of unauthorized migrants. This estimate also includes people who are here legally but are not yet included in the official estimates of legal migrants and refugees. It also includes people in "quasi-legal" status who are awaiting action on their legal migration requests. Because the estimate was derived from a residual methodology, any limitations in the methods or in the measurement of other migration components are reflected in the residual number. In addition, our assumptions include a great deal of uncertainty, especially for small migration components. Therefore, the residual may be quite different from the actual number of unauthorized migrants.

Numbers presented here are based on the entire residual foreign-born population (including some legal populations such as refugees and asylum applicants). Characteristics attributable to the residual foreign born may not be the same as for the unauthorized migrant population.

The DAPE Team estimates 3,765,906 residual foreign born were counted in the 1990 census. Adjusting for an assumed 15-percent net undercount rate, we estimate that as of April 1, 1990 the total residual foreign-born population would be 4,430,478. Adjusting for an assumed 20-percent net undercount rate, the estimated 1990 residual foreign-born population would be 4,707,383.

(Table A-1 of Appendix A shows the total residual foreign-born population as of April 1, 1990 by age, sex, race, and Hispanic origin, but recall that these estimates are not of the unauthorized migrant population.)

The foreign-born population can be depicted as:

FB = L + U

where FB is the total foreign born, and L and U are the legal and unauthorized migrant components, respectively.

The residual foreign-born population in 1990 (R1990) was estimated using the following formula:

R1990 = [R1980 - (E1980-1990 + D1980-1990)] + FB1980-1990 - [(LPR1980-1990 + IRCA1980-1990) - (E1980-1990 + D1980-1990)] - T1987-1990

where a 1980-based estimate of the residual foreign born (R1980) is carried forward to April 1, 1990 through emigration and death. FB is the 1990 Census total foreign born who entered the U.S. between 1980 and 1990. LPR is the legal permanent residents (legal admissions) component for the 1980-1990 period and IRCA refers to the IRCA-legalized population. These two "legal" populations are carried forward to April 1, 1990 through E (emigration) and D (death).11

T refers to temporary migrants (nonimmigrants) who are not affected by emigration or death because they are assumed to be continuously replaced by new temporary migrants of similar characteristics. The years of entry were limited to the past three years (1987-1990) to reflect the short-term residence of most temporary migrants.12

Similar to Method 2 discussed earlier, the DAPE Method uses residual techniques based on the 1990 decennial census, INS data on legal admissions, and components of change. The 1990 census data represent the counted foreign-born population as of April 1, 1990, whereas the latter two components yield the expected legal population at the census date. These include the number of legal migrants (including most refugees who adjusted to LPR status), temporary migrants, and people illegally present who legalized under IRCA,13 deaths to and emigration of legal migrants and the IRCA-legalized population. This technique relies on the simple assumption that the difference between the census-based total foreign-born estimate and the legal population will reflect the size of the residual foreign-born population on the census date.

Adjustments were necessary to address errors in the two primary sets of data, the census data and the INS figures. Any response misreporting, such as citizenship status, through a misinterpretation of the question being asked or through an intentional misrepresentation, is not addressed by this method.

About 900,000 refugees were estimated to have entered the U.S. during the 1980s. Approximately 800,000 adjusted status during this period. The remaining 100,000 are assumed to be included in the residual amount shown here.14

Unauthorized Population Universe

One of the major problems in measuring unauthorized migration is defining the population. Of the unauthorized migrants physically present in the U.S. at any given time, some proportion would not be considered "usual residents" of the United States according to the definitions of enumeration used in the U.S. census. It is assumed that the DAPE Method does not include "sojourner" or "commuter" migrants-people who enter the U.S. for temporary (even daily) lengths of stay. (See Passel (1988) for more information.)

1990 Census Modified Sample File

A 1990 sample file was created for use by all DAPE teams working on international migration components. This file contains race, Hispanic origin, sex, age, place of birth, citizenship status, and other information. Race and Hispanic origin were assigned, based on the 1990 sample file distribution of the foreign born who entered the U.S. between 1980 and 1990, to components that did not have these characteristics.

This allocation method proportionally assigned race and Hispanic origin by place of birth, year of entry, age, and sex of the foreign born.15

People for whom no place of birth was reported (808,158 weighted cases) were assigned a place of birth based on the proportional distribution by state of the foreign-born population with reported place of birth in the 1990 sample file.

The total foreign-born population estimate from the 1990 census file, used in these calculations, is 19,767,316.16 For the purpose of this analysis, the foreign-born population was restricted to those whose year of entry into the U.S. was between 1980 and 1990 (8,663,627).

For the year of entry question on the 1990 census, a multiple-choice format that offered ten pre-determined entry periods of various durations was used. However, the Census 2000 questionnaire provided a write-in field limited to four spaces to represent the actual year of arrival.

Legal Permanent Residents (LPRs) - INS Administrative Records, 1980-199017

The LPR files used for this analysis were created from the INS microdata where some allocations for age and sex have been made. The fiscal year-based INS files (October 1st to September 30th) have been converted to "census years," April 1st to March 31st.

For new arrival cases, year of admission (into legal permanent resident status) was assumed to equal year of entry into the U.S. For adjustees, year of nonimmigrant admission has been used in place of year of admission for year of entry into the U.S. as these people resided in the U.S. prior to obtaining LPR status. Of these cases, anyone with a year of entry prior to 1980 has been excluded from our analysis (542,245 cases).

Although some researchers have questioned the completeness of the records in the INS LPR files (Warren and Passel, 1987), we have not assessed the quality of the INS data for this project. Instead, we recognize that any incompleteness could lead to some legal residents being included in the residual foreign-born estimate.

IRCA-Legalized Population (LAWs (INA Section 245A) & SAWs (INA Section 210))

IRCA-legalized data for our 1990 estimates come from the 1992 Legalization Summary Public Use Tape (LSPUT) file of IRCA LAWs and SAWs, processed through August 12, 1992.18 The file consists of 3,040,948 applications (1,763,434 LAWs and 1,277,514 SAWs). Of these, 1,031,404 LAWs (58.5 percent) and 1,256,015 SAWs (98.3 percent) entered the U.S. between 1980 and 1990. Our 1990 estimate included only those people who were granted LPR status through August 12, 1992 (942,078 LAWs and 1,057,293 SAWs). Our 2000 estimate (described below) included those cases processed throughout the remainder of the 1990s.

For the DAPE Method we assume that all the SAWs were resident in the United States as of Census Day, April 1, 1990. Of the 1.3 million SAW applications for legalization, 9,177 (0.7 percent) had a state of residence outside the 50 States and Washington, DC. (Smith, et al., 1996) Other researchers have taken different approaches to address the issue of whether SAWs were present or not at the time of the census, assuming that some portion of the SAW population (certainly greater than 0.7 percent) was not present in the U.S. at the time of the 1990 census. (Woodrow, 1991; Clark et al., 1994; Bean, 2001)

Pending cases (22,906 LAWs and 18,144 SAWs), who entered the U.S. between 1980 and 1990 are not counted in the IRCA-legalized population for our 1990 estimate, and, therefore, are included in the unauthorized population count for 1990. Denied cases are assumed to be counted in this residual-based foreign-born estimate as well.

Because the age of IRCA applicants was recorded as their age at the date of application, we aged this population two years to the census date, April 1, 1990. The period of application for LAWs was May 5, 1987 to May 4, 1988, and June 1, 1987 to November 30, 1988 for SAWs.

The LSPUT file contains incomplete data on race and Hispanic origin detail for the IRCA-legalized population. Therefore, we have assigned these characteristics, based on the foreign born whose entrance to the U.S. was 1980 to 1990 from the 1990 Census Modified Sample File, by age, sex, country of birth, year of entry, and citizenship status (non-citizens only).

Death to and Emigration of Legal and IRCA-Legalized Populations

Calculations of mortality and emigration rates were based on information provided by the Emigration DAPE Team.19 This team developed the assumptions used for estimating emigration and mortality of the foreign born.

For estimating emigration, rates were assigned by age, sex, race, Hispanic origin, and country of birth. For estimating mortality, for each year of entry (beginning in 1980), survival rates were calculated by age group according to amount of time between year (time) of entry and the census year (for instance, age 0 in mid-year 1980 would have 9.75 years exposure through April 1990).20

Temporary Migrants (Nonimmigrants)21

For the 1990 estimates of international migration, data on temporary migrants come from the 1990 Census Modified Sample file. People were considered to be temporary migrants depending on their education (attainment and school enrollment), industry, occupation, employment status, income, age, year of entry, and household relationship.

Not all countries are included (for example, Cuba and USSR), because people from those countries were assumed to most likely be refugees, and therefore were not counted as temporary migrants.

According to the Temporary Migrant DAPE research, 487,453 temporary migrants were counted in the 1990 census.

1980 Residual Foreign-Born Population Carried Forward to 1990

For our 1980 residual foreign-born population base, we relied on figures that Passel (1988) provided for his 1980 census-enumerated unauthorized population estimates. Passel estimated that about 2.1 million unauthorized migrants were included in the 1980 census (1.1 million men and 1.0 million women).

We allocated age, country of birth, race, and Hispanic origin to this population from the 1990 sample file distribution of the foreign born who entered the U.S. prior to 1980. This estimate was carried forward to April 1990 through emigration and death yielding a residual foreign-born population estimate of 1,770,505.

Some unauthorized migrants, included in the 1980 estimate, would eventually acquire legal status through IRCA in the 1980s. These migrants have not been removed from the 1980 estimate carried forward to 1990, and thus the result is a residual foreign-born rather than an unauthorized population as of 1990.22 (See the Limitations section of this report.)

Undercount Rates

Previous research on estimating unauthorized migration have included varying assumptions about the undercount of the foreign-born population and the rates of undercoverage by legal status. (Passel, 1988; Woodrow, 1991; Bean, 2001) Rates of undercount in the census for the unauthorized population have been assumed to be higher than for the legal population, and have generally fallen between 15 and 20 percent, with undercount rates for men being higher than for women. (Bean, 2001)

Appendix A includes four tables (A-1a, A-1b, A-2a, A-2b) showing our estimated 1990 residual foreign-born population by age, sex, race, and Hispanic origin with assumed rates of undercount at 15 and 20 percent. These rates were simply applied to the residual foreign-born population estimates shown in Table A-1, and were not integrated into the development of the estimates themselves.


Method 3 (2000): DAPE Estimates of the Residual Foreign-Born Population, 2000

The 2000-based estimates of the residual foreign born were calculated using the 1990 methodology (for the 1980 to 1990 period) plus the resulting 1990 estimate carried forward to April 1, 2000. As with the 1990 estimates, unauthorized migrants and quasi-legal migrants (e.g., refugees/asylees not adjusted to LPR status) are included in the residual-based estimate.

Our initial attempt at estimating the quasi-legal migrant population suggests that about 1.7 million (19.5 percent) were included in the residual foreign born estimate for 2000. This estimate includes (estimated number):

Numbers presented here are based on the entire residual foreign-born population (including some legal populations such as refugees and asylum applicants). Characteristics attributable to the residual foreign born may not be the same as for the unauthorized migrant population.

The DAPE Team estimates 8,705,419 residual foreign born were counted in the 2000 census. Adjusting for undercount, we estimate that as of April 1, 2000 the total residual foreign-born population was 10,241,669 (15 percent undercount). This estimate was used for the revised DA estimate for 2000.

(Table A-3 of Appendix A shows the total residual foreign-born population as of April 1, 2000 by age, sex, and race and Hispanic origin, but recall that these estimates are not of the unauthorized migrant population.)

1990 Methodology Applied to 2000

Our 2000 method uses residual techniques based on preliminary 2000 census data, INS data on legal admissions 1990 to 2000,23 and components of change. The 2000 census data represent the counted foreign-born population as of April 1, 2000, whereas the latter two components yield the expected legal population at the census date. These include the number of legal migrants (including most refugees who adjusted to LPR status), temporary migrants, and persons illegally present who legalized under IRCA who were processed after August 12, 1992,24 deaths to and emigration of legal migrants and the IRCA-legalized population. This technique relies on the simple assumption that the difference between the census-based total foreign-born estimate and the legal population will reflect the size of the residual foreign-born population on the census date.

2000 Census Preliminary Sample File

The total foreign-born population estimate from the Census 2000 Preliminary Sample File, used in these calculations, was 31,098,946.25 For the 2000 estimates, the foreign-born population was restricted to those whose year of entry into the U.S. was between April 1990 and March 2000 (12,518,098).

The Census 2000 file used for these estimates (and those of other international migration components in the DAPE project) may differ from final census files processed later in 2001/2002.26

1990 Residual Foreign-Born Population Carried Forward to 2000

The 1990 estimate of 3,765,906 should be reduced due to death (162,830), emigration (391,275), and adjustment of status of the 1990 unauthorized migrants included in the 1990 residual foreign-born population who adjusted throughout the 1990s (about 900,000). However, the population legalizing during the decade was not removed from this 1990 residual foreign-born population carried forward to 2000.27


Limitations

Although the residual technique used to derive estimates of residual foreign born is based on the simple idea of subtracting the expected legal population from the counted foreign-born population at the census date, the approach suffers from a number of limitations. These limitations stem from anomalies and shortcomings in the data sets used, assumptions made to correct for data deficiencies or to derive estimates, and the exclusion of components that may prove to be relevant in the changing migration environment.

Inclusion of Quasi-Legal Migrants in the Residual Foreign-Born Estimate

The most important limitation to the methodology and the resulting estimates described in this report pertains to the inclusion of quasi-legal migrants (e.g., refugees not adjusted for LPR status) in the residual foreign-born estimate. This limitation appears to have a greater impact on the 2000 estimate than on the 1990 estimate. This is actually not a limitation for the use of this estimate in calculating coverage as legal status is not relevant.

Data Quality and Other Data Source Limitations

The precision of our results will depend upon the quality and completeness of the data used, namely the decennial census files, and the administrative records of legal and IRCA-legalized populations provided by the INS.

Other data source limitations include:

Methodological Limitations

Time Constraints

The DAPE project began in late April 2001, and was originally scheduled for completion by July 31, 2001. Extensions were granted through September 10th for the DAPE task of estimating the residual foreign-born population as of 1990 and 2000.

However, lack of detailed, historical documentation on both source files and assumptions and methods led to delays in meeting the milestones of the overall project timeline. In addition, several technical obstacles resulted due to limited documentation.

Comparisons of our 1990 estimates with the official (original) 1990 DA work by Woodrow (1991) could not be made given different data sources and limited time to replicate her CPS-based work while preparing our census and administrative records-based estimates.

Therefore, future work should include a validation of the 1990 DA work by Woodrow, along with additional research into alternative methods and data by other researchers working on this issue. (Espenshade, 1995a; Passel, 1998; Warren, 2000; Bean, 2001)

Impact of Legislation on Migratory Patterns and Quality of Data Collection

Legislation such as IRCA and more recent legislation in the 1990s including the changes to the Immigration & Nationality Act (INA) in 1990 and migration-related legislative changes in 1996 (e.g., Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA) (Pub. L. 104-208); Antiterrorism and Effective Death Penalty Act (AEDPA) (Pub. L. 104-132) impact both migratory patterns and the quality of data collection. Movement across borders (and into legal statuses) are facilitated and impeded by legislation. Data collection instruments and the type of data collected also change with new legislation. These changes, such as with the IRCA legalizations (and related data), affect our estimates as well.

Undercount Rates

Undercount rates are used in this report only for illustrative purposes. Nowhere within this report has there been a comprehensive evaluation of undercount rates for the foreign-born population by legal status or otherwise. Our 1990 and 2000 estimates are shown in Appendix A tables for both census (enumerated) and DA ("true" or resident) levels. In line with contemporary research on undercoverage of the foreign born, undercount rates of 15 and 20 percent (DA level estimates) are presented along with the census-level estimates of the residual foreign-born population as of 1990 and 2000.

From all appearances, the 2000 census is more complete and accurate than 1990. The advertising campaign, partnership programs, and use of the Master Address File (MAF) may have contributed to the improved coverage of the 2000 census.

Assessing the coverage of the foreign-born and both the legal and residual foreign-born populations is important to developing improved estimates of each population. As part of the Post Enumeration Survey (PES) for the 1990 census, undercount rates were not calculated for the foreign born in particular. Race and Hispanic origin-specific rates were derived that can be used to approximate such rates for the foreign born. Harder still is the development of undercount rates by legal status. Again, researchers outside the Census Bureau have analyzed this issue and have provided their own rates by legal status. (Binational Study, 1997; Bean, 2001).

Anecdotal evidence suggests that census coverage improved between the 1990 and 2000 decennial censuses. Hence, undercount rates for the unauthorized migrant population are assumed to have improved between 1990 and 2000.28

IRCA-Legalized Population

Our 1990 residual foreign-born population estimate includes the IRCA-legalized population through August 12, 1992. People granted legal status after April 1, 1990 (but before August 13, 1992) would be included in our 1990 residual-based estimate as legal, thereby reducing the "true" unauthorized population present on Census Day, April 1, 1990.


Results

We put forward estimates of the residual foreign-born population residing in the United States as of April 1, 1990 and April 1, 2000, as shown below in Table 1.

Table 1. Estimates of the Residual Foreign Born, by DA Race and Sex: 1990 and 2000

Subject 1990 2000
Total Male Female Total Male Female
Counted in Census 3765906 1822406 1943500 8705419 4717733 3987686
   Black 293708 150284 143424 611499 317121 294378
   Nonblack 3472198 1672122 1800076 8093920 4400612 3693308
Assumed 15-percent
 Undercount
4430477 2144007 2286470 10241670 5550275 4691395
   Black 345539 176805 168734 719411 373084 346327
   Nonblack 4084938 1967202 2117736 9522259 5177191 4345068
Assumed 20-percent
 Undercount
4707383 2278008 2429375 10881774 5897166 4984608
   Black 367135 187855 179280 764374 396401 367973
   Nonblack 4340248 2090153 2250095 10117400 5500765 4616635

NOTE: This residual foreign-born population is not an estimate of the number of unauthorized migrants. This estimate also includes "quasi-legal" status who are awaiting action on their legal migration requests. Any limitations in the methods or in the measurement of other migration components are reflected in the residual number.

1990 Estimates

According to our calculations shown above in Table 1, the estimated residual foreign-born population counted in the 1990 census was 3,765,906. Assuming a 15-percent undercount rate yields a residual foreign-born population of 4,430,478 in 1990.

Of the 3.8 million, 1.8 million (48.4 percent) were male (Table A-1); 1.2 million (32.8 percent) were ages 18 to 29 (Table A-1); 3.5 million (92.2 percent) were Nonblack (Table A-1); 1.9 million (50.7 percent) were Hispanic (Table A-2); and 1.0 million (26.8 percent) were from Mexico (Table A-7).

2000 Estimates

According to our calculations shown above in Table 1, the estimated residual foreign-born population counted in the 2000 census was 8,705,419. Assuming a 15-percent undercount rate yields a residual foreign-born population of 10,241,669 in 2000.

Of the 8.7 million, 4.7 million (54.2 percent) were male (Table A-3); 3.5 million (40.0 percent) were ages 18 to 29 (Table A-3); 8.1 million (93.0 percent) were Nonblack (Table A-3); 5.4 million (61.5 percent) were Hispanic (Table A-4); and 3.9 million (44.5 percent) were from Mexico (Table A-8).

(See Appendix A for extensive detail by age, sex, race, Hispanic origin, and place (country) of birth for both 1990 and 2000 estimates, but recall that these estimates are not of the unauthorized migrant population.)

Our new 1990 estimate, also with an assumed undercount rate of 25 percent, is 5.0 million, well above the Woodrow 1990 DA figure of 3.3 million.29 To clarify, Woodrow's DA estimate was computed based on November 1989 CPS data, prior to the availability of the 1990 census sample files.

Our estimates are based on a modified 1990 census sample file, and include legal migrants not explicitly accounted for in other legal migrant components of this project.

Comparing the DAPE 1990 and 2000 Estimates with Other Findings (Woodrow, 1991; Ahmed, 1995; Warren, unpublished; Bean, 2001; Passel, 2001)

Although not included here, a comprehensive analysis of our estimates would comprise an evaluation beyond total population counts to include reviews by specific countries of birth, age, sex, race/Hispanic origin, year of entry, and other components of migration (used to derive these estimates).30

Even though the sources used similar techniques, estimates of the size of the residual foreign-born population varied widely. Ahmed (Method 2) placed the figure at 942,000 while Woodrow (Method 1) found the number to be 2.1 million counted in the 1990 census.31

Discrepancies among estimates, in comparing our 1990 estimates with both Ahmed (1995) and Woodrow (1991), can be summarized as follows:

  1. Adjustments for Undercount: Not all methods included an adjustment for undercount of the foreign born or by legal status. Neither the DAPE Method nor Ahmed's make assumptions about undercount in the calculations of the residual foreign-born population. Woodrow (1991) assumes undercoverage in the census and makes allowances for sampling and estimation error in the CPS.

  2. Death and Emigration: Estimates of deaths to and emigration of legal immigrants were calculated for both Method 1 and Method 2, but figures were not always incorporated in the calculations of the residual foreign-born population.

  3. IRCA LAWs and SAWs: The figures for LAWs and SAWs differed greatly from one source to another. These differences may account for significant discrepancies in the estimates of the residual foreign-born population across methods.

  4. Country-Specific (Negative) Estimates: While the range of derived figures for the residual foreign-born population may be plausible, evaluating the total number reveals some inconsistencies. For a number of countries the estimates are negative, and this is true across methods. On the other hand, the derived estimates for other countries seem over-estimated. For example, the Ahmed report places the size of residual foreign-born population from Mexico at about 160,000 or 17 percent, which appears to be low. We estimated that 27 percent of the residual foreign born in 1990 was from Mexico; our 2000 estimate was closer to 45 percent from Mexico. Most studies indicate that Mexico constitutes a substantial proportion of the unauthorized population, around 55 percent. (Warren, 2000; Bean, 2001)

In comparison with our 2000 estimate, Warren (unpublished) suggests 6.7 million unauthorized migrants were counted in the 2000 census, and that when undercount of the foreign born was taken into consideration (by legal status) the unauthorized resident population count rose to 7.6 million.

Bean (2001) estimates about 2.5 million Mexicans were residing in the U.S. in March 1996 yielding an estimated 3.9 million unauthorized migrants from Mexico (when carried forward to March 2000). Through our calculations of the counted residual foreign born in 2000, we estimated 3.9 million Mexicans (44.5 percent of the residual foreign born in 2000).32 Bean also estimates a total unauthorized population of about 7.1 million in 2000.

According to the 1990 residual results, the 18-49 age group accounts for 58 percent of the total population; for the 2000 estimate the proportion of the same age group is 70 percent.

Analysis of the sex structure, on the other hand, shows the number of residual foreign-born women greater than the number of residual foreign-born men in 1990; for the 2000 results, more residual foreign-born men were living in the country. The greater number of women in 1990 was unexpected as migrants were disproportionately male, but it may be attributed to the effect of the IRCA legalization program. Because more men benefited from the amnesty than women and were subsequently allowed to bring their families to the U.S., it is conceivable that the number of residual foreign-born women was higher than the number of residual foreign-born men in 1990. This explanation is consistent with the higher number of Hispanic women aged 18 to 49.


Next Steps - Improvements in Current Approach and Alternative Methods of Measurement

Research will be conducted in the near future on the extent to which the 1990 and 2000 estimates can be revised to more accurately reflect the unauthorized migrant component of the residual foreign-born population. Some minor changes are readily apparent and relatively simple to incorporate into the current methodology.

Our selection of a single method by which to estimate the unauthorized population for the DAPE task should not be misinterpreted as a clear preference for one methodology.

The DAPE project was endeavored to be an "integrated" process. In other words, all of the task teams that were responsible for estimating a single component of international migration (e.g., legal, unauthorized, and temporary migrants, and emigrants) were required to integrate their work (methods, assumptions, and data sources) wherever possible.

Estimates of unauthorized migration (flow) and unauthorized migrants (stock) that use alternative data sources (e.g., apprehensions data (Espenshade, (1995a); 3-Card Method (GAO, 1998)) should be explored to test the validity and reliability of the estimates produced here.

Alternative assumptions and methods developed outside the Bureau should be examined more closely as well. Warren (2000 and unpublished), Bean (2001), and Passel (1998 and 2001) have provided extensive detail on the estimation of the unauthorized population.

Their research provides invaluable information that should be referenced regularly as the Census Bureau revisits its estimates of the residual foreign-born and unauthorized migrant populations.


NOTES:
1 Both the Special Agricultural Workers (SAWs) and pre-1982 entrants (LAWs) were legalized under the Immigration Reform and Control Act of 1986 (IRCA).
2 Assignment of race and Hispanic Origin based on state-specific foreign-born populations would have been a refinement of this allocation technique, given the geographic concentration of the foreign-born population in the U.S. However, this approach was not used due to time constraints of this project.
3 "Residual methods generally were not employed with data collected before the 1980s because the 1980 census was the first decennial census in which a sizable enumerated unauthorized migrant population could be detected through demographic analysis." (Fay, Passel, and Robinson, 1988 cited in Bean, 2001, p. 412)
4 Earlier Census Bureau documentation used such terms as "undocumented," "illegal," or "unauthorized migrants." The methods and the results supporting these documents were actually reflecting the residual foreign-born population.
5 See Woodrow-Lafield, K.A. 1991. "Demographic analysis evaluation project D2: Preliminary estimates of undocumented residents in 1990." (1990 Decennial Census, Preliminary Research & Evaluation Memorandum no. 75) (22 October 1991).
6 This analysis provided the unauthorized population number used for the 1990 DA. The 1990 DA number was used later in the construction of the 2000 DA estimates released in March 2001.
7 Woodrow (1991) suggested that plausible levels of undercoverage in the census were between 20 and 30 percent.
8 A net annual flow of 200,000 unauthorized migrants was used in the Bureau's postcensal population estimates during this period.
9 From the INS IRCA-legalized files, Ahmed selected cases with status granted or pending and having complete information on age, sex, and country of birth, year of entry, and intended state of and county of residence: 1,658,986 LAWs and 1,084,233 SAWs. (Ahmed 1995, pgs. 5-6)
10 When describing the LAW and SAW populations Ahmed takes into account IRCA-legalized people regardless of when they entered the U.S. However, in his calculations (shown in the formulas on pages 1 and 8 of his report) he does not appear to include the pre-1980 entrants, a large segment of the LAW population.
11 No legal migrants are assumed to have become unauthorized during the decade.
12 For more information on the treatment of temporary migrants, see Working Paper #60.
13 Unlike Ahmed's (1995) method (Method 2 here), this method does not include cases pending authorization in the IRCA-legalized population.
14 In evaluating this work in the near future, this "humanitarian" component will be treated separately helping to make possible a more precise estimate of the unauthorized population.
15 For the DAPE work, countries of birth of the foreign born were grouped into 40 countries and regions. (See Appendix A for tables with details by place (country) of birth.)
16 Of the total foreign-born population (all years of entry), 488,570 were in group quarters in 1990.
17 Refer to Working Paper #59 for detailed information on the legal files used in this analysis.
18 The INS discontinued the data system used to process the IRCA-related applications through August 12, 1992. By this time, the INS had processed 3.0 million applications or 88 percent of the LAW and 84 percent of the SAW cases. (Smith, et al., 1996)
19 See Working Paper #62 for detailed information on the emigration and mortality data and assumptions used in this analysis.
20 Persons 100 years of age and above are assumed to have the same mortality rates (by sex).
21 Refer to Working Paper #60 for detailed information on temporary migrants (nonimmigrants).
22 This limitation will also affect the 2000 estimate. (This will be discussed in greater detail later in this report.)
23 INS data on legal immigrants and refugees are available through fiscal year 1999 (September 1999). A population as of April 1, 2000 is needed for our analysis. An October 1999-March 2000 population was estimated using the distributions of the FY 1999 file.
24 The 2000 method picks up where the 1990 method left off with regard to the IRCA-legalized population. As of August 12, 1992, 22,906 LAWs and 18,144 SAWs were pending authorization. With the use of published INS data (INS, 2000), cases identified as pending in the IRCA files were "matched" to actual cases approved post-August 1992. As limited detail was included in the published data, characteristics were assigned to these cases based on IRCA LSPUT information used in the 1990-based estimates. It is assumed that the only reason why these cases were pending was administrative in nature, and, therefore, had no bearing on the applicants' characteristics.25
25 Of the total foreign-born population (all years of entry), 543,435 were estimated to be in group quarters in 2000.
26 Final edit specifications and weighting schemes had not yet been fully developed for use in these preliminary sample files.
27 Beginning in October 1994, section 245(i) of the Immigration & Nationality Act (INA) allowed unauthorized residents who were eligible for legal immigrant status to remain in the U.S. and adjust to permanent resident status by applying at an INS office and paying a fee. Prior to October 1994, most unauthorized residents were required to leave the U.S. and acquire a visa abroad from the Department of State as they are again now. (INS, pA.3-2, 2000)
28 The revised DA estimates used a 15-percent net undercount rate assumption for the residual foreign born in 2000, and a 20-percent net undercount rate assumption for the residual foreign born in 1990.
29 Woodrow's (1991) DA-level estimate of 3.3 million was calculated based on an assumed 25 percent undercount of unauthorized migrants in the 1990 census.
30 Such a review is forthcoming.
31 As mentioned previously, Woodrow did not make use of 1990 census data for her estimates. She estimated the residual foreign-born population as of November 1989 and carried them forward (through emigration and death) to April 1, 1990.
32 Bean assumes that 55 percent of the unauthorized population would be Mexican in 2000.


Appendix A. Tables


Appendix B. Reference Materials: Bibliography

Demographic Analysis-Population Estimates (DAPE) Research Project Reports Related to Evaluating Components of International Migration (in order of Working Paper Series Number)

Deardorff, K. and L. Blumerman. 2001. Evaluating Components of International Migration: Estimates of the Foreign-Born Population by Migrant Status: 2000. (Population Division Working Paper #58) (Release Pending) U.S. Census Bureau.

Perry, M., B. Van der Vate, L. Auman, and K. Morris. 2001. Evaluating Components of International Migration: Legal Migrants. (Population Division Working Paper #59) (Release Pending) U.S. Census Bureau.

Cassidy, R. and L. Pearson. 2001. Evaluating Components of International Migration: Temporary (Legal) Migrants. (Population Division Working Paper #60) (Release Pending) U.S. Census Bureau.

Costanzo, J., C. Davis, C. Irazi, D. Goodkind, R. Ramirez. 2001. Evaluating Components of International Migration: The Residual Foreign Born. (Population Division Working Paper #61) (Release Pending) U.S. Census Bureau.

Mulder, T., B. Guzmán, and A. Brittingham. 2001. Evaluating Components of International Migration: Foreign-Born Emigrants. (Population Division Working Paper #62) (Release Pending) U.S. Census Bureau.

Gibbs, J., G. Harper, M. Rubin, H. Shin. 2001. Evaluating Components of International Migration: Native Emigrants. (Population Division Working Paper #63) (Release Pending) U.S. Census Bureau.

Christenson, M. 2001. Evaluating Components of International Migration: Migration Between Puerto Rico and the United States. (Population Division Working Paper #64) (Release Pending) U.S. Census Bureau.

Cresce, A., R. Ramirez, and G. Spencer. 2001. Evaluating Components of International Migration: Quality of Foreign-Born and Hispanic Population Data. (Population Division Working Paper #65) (Release Pending) U.S. Census Bureau.

Malone, N. 2001. Evaluating Components of International Migration: Consistency of 2000 Nativity Data. (Population Division Working Paper #66) (Release Pending) U.S. Census Bureau.


Census Bureau Technical Documentation Related to Estimating the Residual Foreign-Born Population

Ahmed, B. unpublished. "Estimates of undocumented immigration counted in the 1990 Census." (Draft: March) (U.S. Census Bureau, Population Division).

Costanzo, J. unpublished. "Workshop on estimating unauthorized immigration: Summary." (11 December 1998, Census Bureau, Suitland, Maryland).

Fernandez, E.W. and J.G. Robinson. 1994. "Illustrative ranges of the distribution of undocumented immigrants by state." (Technical Working Paper Series no.8, U.S. Census Bureau, Population Division, Population Estimates and Projections) (October) p.6 (+Appendix).

Goodkind, D. 1999. Measuring International Illicit Migration: An Exploratory Report. (November) U.S. Census Bureau.

Heer, D.M., and J.S. Passel. 1987. "Comparison of two methods for estimating the number of undocumented Mexican adults in Los Angeles County." International Migration Review 21(4): 1446-1473.

Luther, N.Y. and J.S. Passel. 1991. Estimation Of Undocumented Immigration To The United States. (Final Report - Joint Statistical Agreement Between the Bureau of the Census and the East-West Population Institute) (Report No. JSA88-3).

Passel, J.S. and K.A. Woodrow. 1987. "Change in the undocumented alien population in the United States, 1979-1983." International Migration Review 21(4): 1304-1334.

---. 1984. "Geographic distribution of undocumented immigrants: Estimates of undocumented aliens counted in the 1980 Census by state." International Migration Review 18(3): 642-671.

Robinson, J.G. unpublished. "Estimates of undocumented residents." (Internal memo, draft date 26 February 1998) (U.S. Census Bureau).

---. unpublished. "Review of estimates on the size and geographic distribution of the undocumented immigrants." (Written statement to the U.S. Senate-Committee on Appropriations, June 22, 1994).

---. 1980. "Estimating the approximate size of the illegal alien population in the United States by the comparative trend analysis of age-specific death rates." Demography 17(2): 159-76.

Rodriguez, N. and J.S. Hagan. 1991. "Investigating census coverage and content among the undocumented: Ethnographic study of Latin tenants in Houston, Texas." (Ethnographic Evaluation of the Decennial Census Report no.3).

Warren, R. and J.S. Passel. 1987. "A count of the uncountable: Estimates of undocumented aliens counted in the 1980 United States Census." Demography (August) 24(3): 375-393.

Woodrow-Lafield, K.A. 1991. "Demographic analysis evaluation project D2: Preliminary estimates of undocumented residents in 1990." (1990 Decennial Census, Preliminary Research & Evaluation Memorandum no. 75) (22 October 1991).

---. unpublished. "Estimates for the Undocumented Residents in 1990." Internal Memo, U.S. Census Bureau, December 20, Demographic Analysis Evaluation Project D2.

 


Non-Census Bureau Technical Documentation on Measuring the Residual Foreign-Born Population and Unauthorized Migration

1997. Binational Study on Migration Between Mexico and the United States (U.S. Commission on Immigration Reform, Secretaría de Relaciones Exteriores - Coordinators) (F.D. Bean and K. Woodrow-Lafield, authors of Quantification of Migration section) Mexico.

Bean, F. et al. 2001. "Circular, invisible, and ambiguous migrants: Components of difference in estimates of the number of unauthorized Mexican migrants in the United States." Demography 38(3): 411-22.

Briggs, V. 1984. "Methods of analysis of illegal immigration into the United States." International Migration Review 18(3): 623-41.

Clark, R.L. et al. 1994. Fiscal Impacts of Undocumented Aliens: Selected Estimates for Seven States. Washington, DC: Urban Institute.

Delaunay, D. and G. Tapinos. 1998a. La Mesure de la Migration Clandestine en Europe (Volume 2: Rapport des Experts) (Measuring Illegal Migration in Europe) (Eurostat Working Papers, Population et conditions sociales) (3/1998/E/no.7) (English).

---. 1998b. La Mesure de la Migration Clandestine en Europe (Volume 1: Rapport de Synthèse) (Measuring Illegal Migration in Europe) (Eurostat Working Papers, Population et conditions sociales) (3/1998/E/no.7) (French).

Espenshade, T.J. 1995a. "Using INS border apprehension data to measure the flow of undocumented migrants crossing the U.S.-Mexico frontier." International Migration Review 29(2): 545-565.

---. 1995b. "Unauthorized immigration to the United States." Annual Review of Sociology 21: 195-216.

---. 1994. "Does the threat of border apprehension deter undocumented U.S. immigration?" Population Development Review 20(4): 871-92.

Haines, D.W. and K.E. Rosenblum (eds.). 1999. Illegal Immigration in America: A Reference Handbook. Westport, CT: Greenwood Press. p. 573.

Johnson, H.P. 1996. Undocumented Immigration to California: 1980-1993. (September 1996) (http://www.ppic.org/publications/PPIC100/index.html).

La Fondazione Cariplo per le Iniziative e lo Studio sulla Multietnicità (I.S.MU.). 1988. The Fourth Report on Migrations 1998. (Chapter on Illegal Migration by G-C. Blangiardo, Dr. Farina) +methodological appendix (Italian).

Lederer, H.W. 1998. "Illegal migration: Why does it exist and what do we know about numbers and trends?" (Managing Migration in the 21st Century-On the politics and economics of illegal migration, 21-23 June 1998, Hamburg, Germany).

Lowell, B. L. 1992. "Circular mobility, migrant communities, and policy restrictions: Unauthorized flows from Mexico." (U.S. Dept. of Labor, DOL-ILAB Working Paper #13).

Lowell, B.L. and Z. Jing. 1994. "Unauthorized workers and immigration reform: What can we ascertain from employers?" International Migration Review (Fall) 28(3): 427-448.

Passel, J.S. unpublished. "Some random thoughts on undocumented immigration in Census 2000, Demographic Analysis, A.C.E., and the CPS." Mimeo. (2001).

---. unpublished. "Comparison of Demographic Analysis, A.C.E., and Census 2000 Results by Race." (27 February 2001) (Memo to Frances Bourne).

---. 1999. "Undocumented immigration to the United States: Numbers, trends, and characteristics." (in Illegal Immigration in America: A Reference Handbook. Westport, CT: Greenwood Press. p. 27-111.

Passel, J.S. and R.L. Clark, 1998. Immigrants in New York: Their Legal Status, Incomes, and Taxes. Washington, DC: Urban Institute.

Singer, A., and D.S. Massey. 1998. "The social process of undocumented border crossing among Mexican migrants to the United States." International Migration Review 32: 561-92.

Smith, S., R.G. Kramer, and A. Singer. 1996. Effects Of The Immigration Reform And Control Act: Characteristics And Labor Market Behavior Of The Legalized Population Five Years Following Legalization (U.S. Department of Labor, Bureau of International Labor Affairs, Immigration Policy and Research) (May) p.129 (+Appendix).

U.S. General Accounting Office (GAO). 1999a. Illegal Aliens: Significant Obstacles To Reducing Unauthorized Alien Employment Exist. (GAO/GGD-99-33) (April) p.48.

---. 1999b. Survey Methodology: An Innovative Technique for Estimating Sensitive Survey Items. (GAO/GGD-00-30) (November) p.88.

---. 1995a. Illegal Aliens: National Net Cost Estimates Vary Widely. (GAO/HEHS-95-133) (July) p.64.

---. 1995b. Illegal Immigration: INS Overstay Estimation Methods Need Improvement. (GAO/PEMD-95-20) (September) p.68.

---. 1993. Illegal Aliens: Despite Data Limitations, Current Methods Provide Better Population Estimates. (GAO/PEMD-93-25) (August) p.92.

---. 1982. Problems and Options in Estimating the Size of the Illegal Alien Population. (GAO/IPE-82-9) (September 24) p.37.

Warren, R. 2000. Annual Estimates of the Unauthorized Immigrant Population Residing in the United States and Components of Change: 1987 to 1997. (Draft Report, September) (Immigration and Naturalization Service (INS)) http://lamarsmith.house.gov/.

---. 1998. "Unauthorized Immigrants Residing in the United States: Estimated Population, Components of Change, and Trends, by Sex and Broad Area of Origin, 1987 to 1997." (December 11) (draft mimeo as basis for Seminar at U.S. Census Bureau).

---. 1997. Estimates of the Undocumented Immigrant Population Residing in the United States: October 1996. U.S. Department of Justice. Office of Policy and Planning. Immigration and Naturalization Service (INS).

---. 1994. Estimates of the Unauthorized Immigrant Population Residing in the United States, by Country of Origin and State of Residence: October 1992. (Final 20 April 1994) Immigration and Naturalization Service.

Woodrow-Lafield, K.A. 1998. "Undocumented residents in the United States in 1990: Issues of uncertainty in quantification." International Migration Review (Spring) 32(1): 145-73.


Appendix C. Comparing Estimates of the Residual Foreign Born with Estimates Others Have Made of the Unauthorized Migrant Population

Source Estimate
(millions)
Assumed
Undercount
(percent)
Data Year

DAPE (2001 - U.S. Census Bureau)

*8.7 million residual foreign born
(7.0 million unauthorized migrants)

8.7 (7.0)*
(counted)
---
2000
10.2
(incl. underct)
15 %
2000
3.8
(counted)
---
1990
4.7
(incl. underct)
20%
1990
Warren (2001 unpublished)
6.7
(counted)
---

2000

7.6
(incl. underct)

10% (90-00 entrants)
&
5% (pre-90 entrants)

2000
Bean (2001)
7.1
(incl. underct)
15 to 25%
(Mexican Illegal Pop);
assumed higher for males than females
2000 (Total)
3.9
(incl. underct)
2000 (Mex only)
2.5
(incl. underct)
1996 (Mex only)
Woodrow (1991)
- Census Bureau DA, 1990
2.1
(counted)
---
1990
3.3
(incl. underct)
25%
1990
2.8 to 5.0
(incl. underct)

10% to 50%

1990
Passel (1988)
- Census Bureau DA, 1980
2.1
(counted)
---
1980
2.5 to 3.5
(incl. underct)

19 to 38%
(derived)

1980


[PDF] or PDF denotes a file in Adobe’s Portable Document Format. To view the file, you will need the Adobe® Reader® Off Site available free from Adobe.


Source: U.S. Census Bureau, Population Division
Authors: Joe Costanzo, Cynthia Davis, Caribert Irazi,
Daniel Goodkind, and Roberto Ramirez
Questions? / 1-866-758-1060
Created: January 4, 2002
Last Revised: October 31, 2011 at 10:03:10 PM


This symbol Off Site indicates a link to a non-government web site. Our linking to these sites does not constitute an endorsement of any products, services or the information found on them. Once you link to another site you are subject to the policies of the new site.