GAO 

United States Government Accountability Office

Report to the Chairman, Subcommittee 

on Income Security and Family 

Support, Committee on Ways and 

Means, House of Representatives 

U.S. LABOR FORCE 

STATISTICS 

Illustrative 

Simulations of the 

Likely Effects of 

Underrepresenting 

Unauthorized 

Residents 

November 2009 

GAO-10-99 
Page i GAO-10-99 

Contents 

Letter 1

Results in Brief 3 

Agency Comments and Our Evaluation 3 

Appendix I Briefing Slides 8 

Appendix II Comments from the Department of Commerce 56 

Abbreviations 

ACS American Community Survey 

BLS Bureau of Labor Statistics 

CPS Current Population Survey 

DHS Department of Homeland Security 

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 U.S. Labor Force Statistics 
United States Government Accountability Office

Washington, DC 20548 

 

November 30, 2009 

The Honorable Jim McDermott 

Chairman 

Subcommittee on Income Security and 

 Family Support 

Committee on Ways and Means 

House of Representatives 

The Honorable Jim McDermott 

Chairman 

Subcommittee on Income Security and 

 Family Support 

Committee on Ways and Means 

House of Representatives 

Dear Mr. Chairman: 

In times of economic uncertainty as well as in times of stability, 

policymakers and the public rely on labor force statistics, such as the 

unemployment rate, to provide important information on the current state 

of the economy. These statistics, published by the Department of Labor’s 

Bureau of Labor Statistics (BLS), include key figures that are based on 

data obtained from the Current Population Survey (CPS). The CPS, a 

household interview survey administered by the Department of 

Commerce’s U.S. Census Bureau, is designed to represent the entire 

United States civilian noninstitutional population. However, certain U.S. 

residents—specifically, foreign-born persons who are not authorized to 

live here, to whom we refer as unauthorized residents in this report—may 

not be represented in CPS data to the same extent as the general 

population. Little research has been done on whether potential 

underrepresentation of the unauthorized population might noticeably 

affect labor statistics, but policy efforts that depend on valid and reliable 

labor force statistics would benefit from such information. 

In times of economic uncertainty as well as in times of stability, 

policymakers and the public rely on labor force statistics, such as the 

unemployment rate, to provide important information on the current state 

of the economy. These statistics, published by the Department of Labor’s 

Bureau of Labor Statistics (BLS), include key figures that are based on 

data obtained from the Current Population Survey (CPS). The CPS, a 

household interview survey administered by the Department of 

Commerce’s U.S. Census Bureau, is designed to represent the entire 

United States civilian noninstitutional population. However, certain U.S. 

residents—specifically, foreign-born persons who are not authorized to 

live here, to whom we refer as unauthorized residents in this report—may 

not be represented in CPS data to the same extent as the general 

population. Little research has been done on whether potential 

underrepresentation of the unauthorized population might noticeably 

affect labor statistics, but policy efforts that depend on valid and reliable 

labor force statistics would benefit from such information. 

We agreed with your office to examine issues concerning unauthorized 

residents’ impact on labor force statistics. We addressed the following key 

questions: 

1. Extent of underrepresentation: What is known about the extent of any 

underrepresentation of unauthorized residents in CPS data used to 

compile labor force statistics? 

1. Extent of underrepresentation: What is known about the extent of any 

underrepresentation of unauthorized residents in CPS data used to 

compile labor force statistics? 

2. Labor force status: What is known about the likely labor force status 

of unauthorized residents? 

2. Labor force status: What is known about the likely labor force status 

of unauthorized residents? 

3. Possible effects: How might CPS underrepresentation of unauthorized 

residents affect key labor force statistics? 

Page 1 GAO-10-99 U.S. Labor Force Statistics
 

To answer the first two questions, we examined documents and data from 

and interviewed officials from the Census Bureau, the Department of 

Homeland Security, and BLS. We also interviewed and obtained data from 

immigration and statistical experts outside these agencies (see slide 44 in 

app. I for a listing of these experts and their roles). Additionally, we 

reviewed previous GAO work and other studies on unauthorized residents, 

government surveys, and labor force statistics and interviewed 

immigration advocates about these topics. To answer the third question, 

we conducted simulations to illustrate how undercounting unauthorized 

residents may have affected the unemployment rate, size of the U.S. labor 

force, and number of employed persons in March 2008. We determined 

that March 2008 was the most recent time period for which data were 

available that were sufficiently reliable for the purposes of our main 

simulations. We created the simulated statistics by first using 

combinations of assumptions obtained from experts about the extent of 

underrepresentation of unauthorized residents and their level of 

unemployment in March 2008. Then, because the estimates obtained from 

experts were uncertain, we used much broader assumptions to test the 

robustness of our results. We compared all of the simulated statistics with 

the margins of error for the original statistics. We also updated these 

simulations using June 2009 national labor force statistics as a test of 

whether changing economic conditions might affect our results.1

We conducted our work from November 2008 to November 2009 in 

accordance with all sections of GAO’s Quality Assurance Framework that 

are relevant to our objectives. The framework requires that we plan and 

perform the engagement to obtain sufficient and appropriate evidence to 

meet our stated objectives and to discuss any limitations in our work. We 

believe that the information and data obtained, and the analysis 

conducted, provide a reasonable basis for any findings and conclusions. 

 

1

After March 2008, the month of our detailed simulations, the U.S. unemployment rate rose, 

reaching 9.5 percent in June 2009. Declining economic conditions may affect the number of 

unauthorized residents in the United States, although recent estimates of the size of this 

population are not available. With this in mind, we performed sensitivity analyses that 

included decreasing the size of the unauthorized labor force (represented in the CPS data) 

by up to 30 percent. The sensitivity analyses indicated that a decrease of this magnitude 

would not change our simulation findings. 

Page 2 GAO-10-99 U.S. Labor Force Statistics
 

On October 2, 2009, we briefed your staff on the results of our work. This 

report formally conveys the information provided during that briefing (see 

app. I for the briefing slides). In general, we found the following: 

• The extent of CPS underrepresentation of unauthorized residents is 

unknown, but experts we consulted told us that the CPS data might not 

represent approximately 10 to 15 percent of unauthorized residents. 

• Little information is available about the labor force status of unauthorized 

residents, but experts we consulted suggested that their approximate 

unemployment rate in March 2008 may have been 6.5 to 8.5 percent, 

compared with 5.2 percent nationally. 

• Little is known about the effect of underrepresentation of unauthorized 

residents on labor force statistics. However, using the above information 

provided by experts, we simulated the likely effects of adding 

unauthorized residents assumed not represented in March 2008 labor force 

statistics. Because the expert assumptions were uncertain, we tested our 

results using a broader range of assumptions. Our simulations showed that 

adding unauthorized residents not represented in CPS data would likely 

have a minimal effect on the overall U.S. unemployment rate. The 

simulations did not, however, rule out the possibility that adding such 

residents would increase the estimated size of the national labor force and 

the estimated number of persons employed nationally. Updating these 

simulations using national labor force statistics for June 2009 revealed 

similar effects. 

Prior to our October 2, 2009, briefing, we provided the Departments of 

Labor, Homeland Security, and Commerce with a draft of the briefing 

document and incorporated technical comments provided by the Bureau 

of Labor Statistics and the Census Bureau as appropriate. Homeland 

Security had no comments on the slides. Since then, Labor, Homeland 

Security, and Commerce have reviewed a draft of this report. Homeland 

Security had no comments, and BLS informally remarked positively on the 

way that our draft accounted for uncertainty related to unauthorized 

workers. Commerce provided written comments, reproduced in appendix 

II, which did not dispute any of our three main findings concerning the 

possible impacts of underrepresentation of unauthorized residents on 

national labor force statistics. However, Commerce suggested that we 

(1) further explicate how survey data are weighted to improve statistical 

representation and how we conducted our simulations, as well as 

providing—in this letter—more specifics about the experts we consulted; 

(2) remove information on the two-card (or “grouped answers”) approach 

Results in Brief 

Agency Comments 

and Our Evaluation 

Page 3 GAO-10-99 U.S. Labor Force Statistics
 

for estimating the number of illegal immigrants represented in a survey, 

because including it implies both that this method is appropriate for use in 

the CPS and that it can be used to estimate underrepresentation;2

 and 

(3) reduce the range of underrepresentation in our illustrative simulations, 

which we vary from 0 to 50 percent, because Commerce stated that using 

this range gives the range more plausibility than is supported by research. 

In response to Commerce’s first suggestion, we added some additional 

information to the slides. One new footnote cites a Census Bureau 

publication that provides detailed information on how CPS data are 

weighted, and another new footnote provides a numerical illustration of 

how we conducted our simulations. We also added a parenthetical note in 

this letter, indicating the slide that lists the experts we consulted and their 

roles, and clarified that we consulted experts in both immigration and 

statistics. 

In response to Commerce’s second suggestion, we did not change our 

presentation of information on the grouped answers method for the 

following reasons: 

• Our slide presentation clearly states that the grouped answers method is 

appropriate for a survey conducted by a private-sector organization. 

Consistent with Commerce’s comments, we concluded in our September 

2006 report3

 on estimating the unauthorized population that the grouped 

answers method is not appropriate for any existing government-conducted 

survey, including the CPS; the 2006 report therefore raised the possibility 

of a new survey designed for the foreign-born population. If the grouped 

answers method were validated and included in a private-sector survey of 

the foreign-born, the resulting data logically could be used to help assess 

statistics based on a government-conducted general population survey 

such as the CPS, as well as serve various other policy and evaluation 

purposes.4

 

2

The grouped answers method is described in slides 41 to 43 in appendix I of this report. 

3

GAO, Estimating the Undocumented Population: A “Grouped Answers” Approach to 

Surveying Foreign-Born Respondents, GAO-06-775 (Washington, D.C.: Sept. 29, 2006). 

4

For example, data on a respondent’s legal status (such as legal permanent resident or 

refugee) are not collected by government-conducted general-purpose surveys such as the 

CPS—but potentially could be collected by a private-sector survey using an approach such 

as the grouped answers method. Such data are relevant to implementing various laws and 

evaluating various immigration policies. 

Page 4 GAO-10-99 U.S. Labor Force Statistics
 

• While the grouped answers method is not intended to estimate 

underrepresentation, if validated and used in a new private-sector survey, 

it could provide information on specific groups within the foreign-born 

population (such as the number of employed unauthorized workers and 

the number of unauthorized workers in the labor force). Such data would 

be useful to the task addressed in this report in at least two ways. First, in 

the illustrative simulations we conducted, we made assumptions about 

unemployment levels within the unauthorized worker population because 

there was no survey estimate of unemployment for this group. The 

grouped answers method, applied in a new private-sector survey, might 

provide such an estimate. Second, our illustrative simulations used an 

indirect estimate of the unauthorized worker population represented in 

the CPS; this indirect estimate had been produced by a researcher using a 

subtraction method (see slide 12 of app. I) and various assumptions 

regarding labor force status in this group. A private-sector survey using the 

grouped answers method could help researchers using the subtraction 

method or other indirect methods by, for example, providing a survey 

estimate of the number of unauthorized workers represented in a privatesector survey.5

Regarding Commerce’s third suggestion, we did not reduce the range of 

the test assumptions for underrepresentation of unauthorized workers in 

the CPS. Our reasons are that this report (1) already presents analyses that 

use fairly narrow ranges of assumptions deemed most plausible by experts 

(for both underrepresentation and unemployment among unauthorized 

workers) and (2) uses much broader ranges of 0 to 50 percent to test 

results produced using the fairly narrow ranges. We conducted the test 

simulations because of uncertainty about the narrower expert-based 

ranges. Specifically, using alternative assumptions of 0 to 50 percent, we 

tested how far “off the mark” the expert assumptions would have to be for 

our findings to change. Our tests show that the initial expert-based 

narrow-range results would hold up even if the expert-based assumptions 

were rather far off the mark. 

 

5

Additionally, because the subtraction method estimates the unauthorized population by 

subtracting estimates of immigrants in specific legal status categories from an overall 

estimate of the total foreign-born population, researchers using this approach would be 

helped by grouped answers estimates of foreign-born persons in specific legal status 

categories (such as the number of legal permanent residents). The grouped answers 

method could provide direct estimates of these categories. 

Page 5 GAO-10-99 U.S. Labor Force Statistics
 

Finally, Commerce provided additional information about correspondence 

between GAO and the Census Bureau concerning an open GAO 

recommendation.6

 This recommendation dates from 1998 and concerns 

devising a plan of research for evaluating the quality of census and survey 

data on foreign-born persons. There have been various communications in 

addition to the letter referenced by the Census Bureau,7

 but the Census 

Bureau has not proposed a strategy or plan of research for evaluating the 

quality of census and survey data on foreign-born persons. Innovative 

thinking and collaboration may be required to make progress on this longterm recommendation. For example, one approach may be for the Census 

Bureau to design research and evaluation options that it might pursue in 

partnership or coordination with others (such as other federal agencies, 

universities, or private-sector organizations). 

As agreed with your office, unless you publicly announce its contents 

earlier, we plan no further distribution of this report until 7 days from the 

report date. We will then send copies of this report to relevant 

congressional committees, the Secretary of Labor, the Secretary of 

Commerce, the Secretary of Homeland Security, and other interested 

parties. In addition, this report will be available at no charge on GAO’s 

Web site at http://www.gao.gov. 

 

6

GAO, Immigration Statistics: Information Gaps, Quality Issues Limit Utility of Federal 

Data to Policymakers, GAO/GGD-98-164 (Washington, D.C.: July 31, 1998). 

7

Perhaps most notably, in addition to the letter mentioned by the Census Bureau, we 

outlined various possible approaches that Census might take in estimating undercoverage 

of foreign-born persons, including a new record linkage (data-matching) approach. We 

shared this information with Census Bureau staff at a meeting and subsequently discussed 

this and other possible methods with them during 2008. We also made additional 

suggestions in a February 2009 letter to the Census Bureau. 

Page 6 GAO-10-99 U.S. Labor Force Statistics
 

If you or your staff have any questions about this report, please contact 

either Nancy Kingsbury at (202) 512-2700 or kingsburyn@gao.gov or 

Cornelia Ashby at (202) 512-7215 or ashbyc@gao.gov. Contact points for 

our Offices of Congressional Relations and Public Affairs may be found on 

the last page of this report. GAO staff who made key contributions to this 

report are listed on slide 47 of appendix I. 

Sincerely yours, 

ancy Kingsbury 

Managing Director, Applied 

ethods 

Cornelia M. Ashby 

Director, Education, Workforce, 

 and Income Security Issues 

N

 Research and M

 

Page 7 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

Page 8 GAO-10-99 

Appendix I: Briefing Slides 

1

U.S. Labor Force Statistics: Illustrative 

Simulations of the Likely Effects of 

Underrepresenting Unauthorized Residents

Briefing for Staff of Chairman Jim McDermott 

Subcommittee on Income Security and Family Support 

House Committee on Ways and Means 

October 2, 2009

Prepared by GAO’s Applied Research and Methods and Education, 

Workforce, and Income Security Teams

 U.S. Labor Force Statistics 
Appendix I: Briefing Slides 

2

Introduction

Labor force statistics are economic benchmarks for policymakers and 

the general public.

• The Labor Department’s Bureau of Labor Statistics (BLS) 

produces key statistics, such as the unemployment rate, the 

size of the labor force, and the number of employed persons.

• BLS compiles these statistics using data from the Current 

Population Survey (CPS), a monthly household interview 

survey that is designed and weighted to represent the U.S. 

population as measured by updated census counts. 

• The CPS is intended to represent the entire civilian 

noninstitutional population, including those foreign-born 

persons who are not authorized to reside in the United 

States.

Page 9 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

3

Introduction (cont.)

CPS data may represent many—but likely not all—unauthorized 

foreign-born residents.1

• CPS data differentiate between native and foreign-born 

persons, but not between the foreign-born who reside here 

legally and those who reside here illegally (referred to as 

unauthorized residents in this briefing). 

• Indirect analyses suggest that millions of unauthorized 

residents may be represented in CPS data.2

• Some additional unauthorized residents may not be 

represented in these data.

1Foreign-born residents include naturalized citizens, other authorized persons, and unauthorized residents.

2See, for example, Jeffrey S. Passel and D’Vera Cohn, A Portrait of Unauthorized Immigrants in the United States, 

(Washington, D.C.: Pew Hispanic Center, Apr. 14, 2009). 

Page 10 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

4

Introduction: Effects of Underrepresentation

The effect that underrepresenting unauthorized residents may have 

on CPS-based labor force statistics depends on two key factors:

• The number of unauthorized residents who are not 

represented in CPS data. For example, if this number is small 

compared with the general population, then omitting data on 

them would probably have a small effect. 

• The labor force status of unauthorized residents who are 

not represented in CPS data. For example, if this group’s 

employment status is similar proportionately to that of the 

general population, then omitting data on them would have 

little effect on some statistics, such as the unemployment rate.

Page 11 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

5

Key Questions 

For this briefing, we examined these questions:

1. EXTENT OF UNDERREPRESENTATION: What is known 

about the extent of any underrepresentation of unauthorized 

residents in CPS data used to compile labor force statistics?

2. LABOR FORCE STATUS: What is known about the likely 

labor force status of unauthorized residents?

3. POSSIBLE EFFECTS: How might CPS underrepresentation 

of unauthorized residents affect key labor force statistics? 

Page 12 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

6

Scope and Methodology

To obtain background information and answer questions 1 and 2, we: 

• Examined documents and data from the Department of 

Commerce’s Census Bureau, the Department of Homeland 

Security (DHS), and BLS.

• Reviewed existing GAO work.

• Interviewed federal officials, immigration experts, and immigrant 

advocates about unauthorized residents and employment.

• Examined selected academic and policy institute studies of 

unauthorized residents, government surveys, and labor 

statistics.1

1We selected studies on the basis of their relevance to our work.

Page 13 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

7

Scope and Methodology (cont.)

• To answer our third question: 

• We conducted simulations to illustrate how underrepresenting 

unauthorized residents might have affected three BLS statistics in 

March 2008:1

• unemployment rate; 

• size of the U.S. labor force; and

• number of employed persons.

• We updated this analysis using the more limited data available for 

June 2009.

• For these analyses, we obtained ranges of possible effects by varying 

our assumptions about the 

• extent of underrepresentation of unauthorized residents and 

• level of unemployment for unauthorized residents who were not 

represented in CPS data.2

• See appendix A for more information on our methods.

1March 2008 is the most recent time period for which an expert has published estimates of not only the 

unauthorized population, but also the number of unauthorized workers.

2We determined that the data we used were sufficiently reliable for the purposes of our simulations.

Page 14 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

8

Scope and Methodology (cont.)

• We did not focus on

• statistics for local areas, specific occupations, or economic sectors;

• trends in labor force statistics over time; or

• other data sources for labor statistics, besides the CPS. (See app. B.)

• We provided a draft of this briefing to the Departments of Labor, 

Commerce, and Homeland Security for review. Within these departments, 

BLS and the Census Bureau provided technical comments that we 

incorporated as appropriate. DHS had no comments. 

• We conducted our work from November 2008 to October 2009 in 

accordance with all sections of GAO’s Quality Assurance Framework that 

are relevant to our objectives. The framework requires that we plan and 

perform the engagement to obtain sufficient and appropriate evidence to 

meet our stated objectives and to discuss any limitations in our work. We 

believe that the information and data obtained, and the analysis conducted, 

provide a reasonable basis for any findings and conclusions.

Page 15 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

9

Summary of Findings

1. UNDERREPRESENTATION: The extent to which unauthorized residents 

are underrepresented in CPS data is unknown, but experts we consulted 

suggested this might range from 10 to 15 percent.

2. LABOR FORCE STATUS: Little is known about unauthorized residents’

labor force status, but experts we consulted suggested that their 

unemployment rate may have been between 6.5 and 8.5 percent in March 

2008, versus a national rate of about 5.2 percent. 

3. POSSIBLE EFFECTS: Our simulations for March 2008 and update for 

June 2009 indicated that, despite uncertainties,

• adding unauthorized residents not represented in CPS data would 

likely have a minimal effect on the U.S. unemployment rate, but

• increases to the estimated size of the U.S. labor force or the 

estimated number of employed persons cannot be ruled out.

Page 16 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

10

Labor Force Statistics

• BLS is the source of government labor force statistics, which 

include but are not limited to the following:

• Unemployment Rate: 

Percentage of the labor force that is not working and is 

looking for work.

• Labor Force Size: 

Number of persons who are working or looking for work.

• Employed Persons: 

Number of persons who are working.1

• BLS bases these three statistics on CPS data.

• BLS reports statistics at the national and state levels.

Background

1BLS publishes two estimates of employment: (1) the number of persons employed, measured by the CPS, 

and (2) the number of jobs, measured by the Current Employment Statistics survey. We focus here on the CPS 

estimate only.

Page 17 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

11

The Current Population Survey (CPS)

• The Census Bureau administers the CPS monthly to approximately 

60,000 households.

• The CPS asks a household member to report characteristics of 

each individual in the household, including country of birth, as well 

as overall household characteristics. BLS bases its labor force 

statistics on CPS data for those aged 16 and older.

• The CPS does not ask about authorization to reside or work in the 

United States. BLS officials told us that asking about legal status 

could discourage cooperation with the CPS.

• The Census Bureau takes several steps to minimize 

underrepresentation in the CPS and increase its accuracy. See 

appendix C for more information.

Background

Page 18 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

12

Almost 12 Million Unauthorized Residents Are 

Estimated to Reside in the United States

DHS and the Pew Hispanic Center have estimated the number of 

unauthorized residents by using existing data on foreign-born U.S. 

residents. Essentially, DHS and Pew have

• begun with an estimate of the number of all foreign-born 

persons residing here (including both those who are and those 

who are not authorized to live in the United States);1

• subtracted the number who are authorized to reside here;2

• made various assumptions about, for example, the effects of 

underrepresentation; and

• concluded that in early 2008, almost 12 million residents—

approximately one-third of all foreign-born—were unauthorized.

Background

1The Pew Hispanic Center estimates this using data from the CPS, while DHS uses data from another national

survey, the American Community Survey.

2This number, estimated using primarily DHS data, includes persons such as legal permanent residents and refugees.

Page 19 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

13

Previous GAO Work

In 1998, we reported that policymakers need reliable information on 

foreign-born persons for policy-related activities and decision making, 

but such data were not available (GAO/GGD-98-164).

• We recommended that the Census Bureau and DHS publish a 

plan of research to evaluate census and survey data on the 

foreign-born. 

• Given continued interest by Members of Congress in related 

issues, we continue to follow up on agency efforts in this area.

• We are working with Census Bureau officials to plan a meeting 

to discuss letters we exchanged in 2008 and 2009 concerning 

difficulties that the Census Bureau anticipates in implementing 

some approaches to evaluating representation of the foreignborn. 

Background

Page 20 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

14

Previous GAO Work (cont.)

• In 2004, we reported that lack of data precluded us from estimating 

the cost of educating children who are not authorized to reside in 

the United States (GAO-04-733).

• In 2006, we reported that foreign-born respondents appear to 

accept an innovative method of asking about legal status in 

personal interviews conducted by a nongovernment entity (GAO06-775).1 

Background

1This survey approach groups legal statuses in boxes on a flash card. Each foreign-born respondent chooses 

the box containing his or her legal status, along with other statuses. No one specifically chooses the 

unauthorized status. See appendix D for more details.

Page 21 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

15

The Extent of Underrepresentation Is Unknown, 

but Some Experts Suggest 10 to 15 Percent

• Information on the number of unauthorized residents who are not 

represented in CPS data is unavailable.

• Three experts told us that 10 to 15 percent of unauthorized 

residents might not be represented in CPS data, but these figures 

are uncertain.1

• One of the experts, Jeffrey S. Passel of the Pew Hispanic Center, 

used analytic procedures to estimate that the underrepresentation 

of unauthorized residents in the March 2008 CPS was 

approximately 12.5 percent. 

• Passel applied Census Bureau estimates of undercounts for the 

overall U.S. population in 2000, by race, age, and gender, to 

foreign-born CPS respondents. He assumed higher undercount 

rates for recent and unauthorized immigrants.2

Finding 1: Underrepresentation

1These experts were Steven A. Camarota, Michael D. Hoefer, and Jeffrey S. Passel. See appendix E. 

2We use the term "undercount" when referring to census counts of the population and the term 

"underrepresentation" when referring to statistics based on data from a sample survey, such as CPS.

Page 22 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

16

• The figures for the underrepresentation of unauthorized residents 

cited in this briefing are uncertain, because they rely on inferences 

based on demographic characteristics and/or a single study with 

limited scope. For example, the three experts we consulted on 

underrepresentation all referred to a key study that attempted to 

measure the size of the census undercount of unauthorized 

Mexicans in Los Angeles County.1

• In our analyses, we first simulated underrepresentation as ranging 

from 10 to 15 percent. Then, because the expert figures were 

uncertain, we tested the robustness of our results by broadening

this range to 0 to 50 percent.

• Note: The experts estimated the 10 to 15 percent range for the 

entire unauthorized population. To conduct our simulations, 

we applied this range to unauthorized residents in the labor 

force.

Finding 1: Underrepresentation (cont.)

1See Enrico A. Marcelli and Paul M. Ong, Estimating the Sources of the 2000 Census Undercount among 

Foreign-born Mexicans in Los Angeles County (prepared for the Annual Population Association of America 

meetings, Atlanta, Georgia, May 10, 2002).

Page 23 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

17

Little Is Known about the Labor Force Status of 

Unauthorized Residents

• Labor force status includes

• having a job (employed);

• having no job and looking for work (unemployed); and

• having no job and not looking for work (out of the labor force),

such as homemakers, retirees, and “discouraged workers.”

• Limited information is available on whether the labor force status of 

unauthorized residents who are not represented in CPS data differs 

from that of 

• unauthorized residents represented in the CPS or

• the overall, general population of the United States. 

• Passel estimated that in March 2008, there may have been about 

8.3 million unauthorized residents in the U.S. labor force.1

Finding 2: Labor Force Status

1This estimate includes an upward adjustment for assumed underrepresentation. Passel’s figure before 

adjusting for underrepresentation was 7.2 million.

Page 24 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

18

• Passel and two other experts who provided input on unemployment among 

unauthorized residents told us the following: 

• The unemployment rate of unauthorized residents is likely to vary over 

time and be affected by changes in the economy and government 

policies.

• The unemployment rate for unauthorized residents might have been

between 6.5 and 8.5 percent in March 2008, higher than BLS’s

reported rate of about 5.2 percent for the general population. However, 

these figures are uncertain.1

• In our simulations of the unemployment rate and number employed, we 

first assumed March 2008 unemployment rates for unauthorized residents 

of 6.5 to 8.5 percent. Then, because the expert figures were uncertain, we 

broadened this range to 0 to 50 percent to test the robustness of our 

results. 

Finding 2: Labor Force Status (cont.)

1These experts were Steven A. Camarota, Randy Capps, and Jeffrey S. Passel. The figures they provided are 

marked by varying degrees of uncertainty because they rely on assumptions and inferences, such as using 

CPS data on all immigrants from Mexico and Central America as a proxy population for unauthorized residents.

Page 25 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

19

• Some experts suggested to us that the effect of underrepresenting 

unauthorized residents on overall statistics would likely be small. However, due 

to a lack of data, experts ultimately do not know the effect of 

underrepresentation on labor force statistics. 

• Our simulations focused primarily on three March 2008 statistics:1

• unemployment rate (U.S. reported figure: 5.2 percent), 

• size of the labor force (U.S. reported figure: 153.1 million), and 

• number of employed persons (U.S. reported figure: 145.1 million). 

• We also conducted rough simulations to determine whether similar patterns of 

results might hold for June 2009.2

• To test whether including unauthorized residents who were not represented in 

CPS data would change the three statistics listed above, we recalculated them 

using various assumptions about

(1) the underrepresentation of unauthorized residents and

(2) the unemployment rate of those who were not represented.

Finding 3: Possible Effects

1In this briefing, we use labor force statistics that are not seasonally adjusted.

2Our simulations cannot be generalized to other time frames without further analysis. 

Experts Do Not Know the Effect of Underrepresentation; Some Suggest It May Be Minimal

Page 26 GAO-10-99 U.S. Labor Force Statistics
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20

Unemployment Rate: Likely Effect of 

Underrepresentation Was Minimal

• According to BLS data, the March 2008 national unemployment rate was 5.24 

percent. The margin of error for this statistic is +/- 0.17 percent.1

• We conducted two sets of simulations for March 2008:

• In the first set of simulations, we varied underrepresentation from 10 to 15 

percent and varied unemployment rates for the unauthorized residents not 

represented in the data from 6.5 to 8.5 percent.

• In the next set of simulations, we used a broader range for 

underrepresentation (0 to 50 percent) and unemployment rates (0 to 50 

percent) to test the robustness of the initial results.

• The first set produced simulated unemployment rates that fell within the margin 

of error of BLS’s reported rate (5.24 percent, +/-0.17 percent), which we regard 

as a minimal effect. 

• In the second set, only assumptions considerably more extreme than the 

ranges suggested by experts produced simulated unemployment rates that fell 

outside BLS’s margin of error. See figure 1.

Finding 3: Possible Effects (March 2008)

1BLS' published estimate is 5.2 percent, but we are providing a more precise figure for purposes of comparison 

with simulated values and margins of error. The margins of error used in this briefing correspond to 90 percent 

confidence intervals around BLS’s reported statistics.

Page 27 GAO-10-99 U.S. Labor Force Statistics
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21

Figure 1: Simulated U.S. Unemployment Rates after Including Unauthorized 

Residents Assumed Not Represented in CPS Data, March 2008 

Finding 3: Possible Effects (March 2008)

Page 28 GAO-10-99 U.S. Labor Force Statistics
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22

Labor Force: Potential Increases Cannot Be 

Ruled Out

• BLS estimated that the March 2008 national labor force size was 153 million. The 

margin of error for this figure is about +/- 506,000.

• For our simulations for March 2008, we assumed that the BLS estimate of 153 million 

includes 7.2 million unauthorized members of the labor force. 

• For our first set of simulations for this time period, we further assumed that the 7.2 

million figure underrepresented unauthorized members of the labor force by 10 to 15 

percent. The resulting simulations added 800,000 to 1.3 million more unauthorized 

members of the labor force to the BLS figure of 153 million, for a simulated total of 

roughly 154 million. 

• Our second set of simulations for this time period explored a broader range of 

assumptions for underrepresentation (0 to 50 percent). These simulations added 0 to 

7.2 million to the BLS figure of 153 million, for simulated totals ranging from 153 to 160 

million.

• Most simulations produced simulated national labor force sizes that were above the 

margin of error of BLS’s reported labor force size.1

Finding 3: Possible Effects (March 2008)

1 The simulated labor force size fell within the margin of error only in simulations with assumed 

underrepresentation of less than 7 percent. We provide this information as an observation; we have not 

conducted formal tests of significance.

Page 29 GAO-10-99 U.S. Labor Force Statistics
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23

Employed Persons: Potential Increases Cannot 

Be Ruled Out

• In March 2008, BLS estimated that there were 145 million employed 

persons. The margin of error was about +/- 541,000.

• Our simulations for March 2008 assumed, as on the previous slide, that the 

BLS labor force estimate of 153 million persons included 7.2 million 

unauthorized residents. 

• In the first set of simulations:

• As on the previous slide, we varied underrepresentation from 10 to 15 

percent, adding from 800,000 to 1.3 million unauthorized residents to 

the labor force.

• We then assumed that from 6.5 to 8.5 percent of the added 

unauthorized residents were unemployed, meaning that 91.5 to 93.5 

percent were employed; we applied these percentages to the 800,000 

to 1.3 million added to the labor force. 

• Resulting simulations added 700,000 to 1.2 million employed persons 

to the BLS figure of 145 million, for a simulated total of roughly 146 

million. 

Finding 3: Possible Effects (March 2008)

Page 30 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

24

• In the next set of simulations:

• As before, we used a broader range of assumptions for 

underrepresentation (0 to 50 percent), adding from 0 to 7.2 

million to the labor force.

• We then assumed that 0 to 50 percent of the added 

unauthorized residents were unemployed, or that 50 to 100 

percent were employed, and applied these employed 

percentages to the 0 to 7.2 million added to the labor force. 

• These simulations added from 0 to 7.2 million employed 

persons to the BLS figure, for simulated totals ranging from 145

to 152 million. 

• Most simulations produced simulated numbers of employed 

persons that were above the margin of error of BLS’s reported 

national figure.1 See figure 2.

Finding 3: Possible Effects (March 2008)

1The simulated number of employed persons fell within the margin of error of the reported statistic for a fairly narrow range of

assumptions, including (1) underrepresentation of less than 8 percent or (2) underrepresentation of less than 9 percent and

an unemployment rate of more than 13 percent. This is provided as an observation; we did not conduct formal tests of significance.

Page 31 GAO-10-99 U.S. Labor Force Statistics
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25

Figure 2: Simulated U.S. Employed Persons after Including Unauthorized 

Residents Assumed Not Represented in CPS Data, March 2008 

Finding 3: Possible Effects (March 2008)

Page 32 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

26

• After March 2008, the month of our detailed simulations, the U.S. 

unemployment rate rose, reaching 9.5 percent in June 2009, and two experts 

told us that the rate for unauthorized residents may have risen more steeply 

over this time period, perhaps to 11 or even 15 percent.

• While more recent estimates of size of the overall unauthorized population are 

not available, one expert believes this population may have decreased due to 

declining economic conditions, and another thinks its size has stayed roughly 

the same.1

• We performed simulations of the effects of underrepresentation on June 2009 

labor force statistics for which we assumed no change since March 2008 in the 

size of the unauthorized labor force represented in CPS data.

• As a check, we also performed sensitivity analyses in which we increased 

and decreased the size of the unauthorized labor force (represented in the 

CPS data) by up to 30 percent. The sensitivity analyses indicated that 

changes of this magnitude would not change our simulation findings.

Finding 3: Possible Effects (June 2009)

1See Jeffrey S. Passel and D’Vera Cohn, Mexican Immigrants: How Many Come? How Many Leave? (Washington, 

D.C.: Pew Hispanic Center, July 22, 2009), and Steven A. Camarota and Karen Jensenius, A Shifting Tide: Recent 

Trends in the Illegal Immigrant Population (Washington, D.C.: Center for Immigration Studies, July 2009).

Effects of Underrepresentation May Be Similar 

under More Recent Economic Conditions

Page 33 GAO-10-99 U.S. Labor Force Statistics
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27

• Our simulations for June 2009 were approximate, or rough, in that 

we used the broad assumptions of 0 to 50 percent 

underrepresentation of unauthorized residents and 0 to 50 percent 

unemployment for this group without identifying a narrower range of 

potentially more likely values based on expert opinion.

• We found patterns in our June 2009 simulations similar to our 2008 

results. 

• Barring extreme assumptions or other differences we were not able 

to measure, underrepresentation may have had similar effects on 

2008 and 2009 statistics.1

Finding 3: Possible Effects (June 2009)

1Our findings for both years are consistent with much earlier analyses that adjusted for census undercoverage for the overall 

population. See Courtenay M. Slater, “The Impact of Census Undercoverage on Federal Programs,” in Conference on 

Census Undercount: Proceedings of the 1980 Conference (Washington, D.C.: U.S. Bureau of the Census, 1980), 107-111).

Page 34 GAO-10-99 U.S. Labor Force Statistics
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28

Effects of Underrepresentation May Be Larger in 

Some States

We did not simulate state-level labor force statistics, but our research 

indicates the following:

• Unauthorized residents probably represent a higher percentage

of the population in certain states.

• In some cases (e.g., Arizona, California, and Nevada), the 

percentage may be about twice as high as the national figure.

• Additionally, some experts believe that the underrepresentation

of unauthorized residents is greater in certain states.

• Effects on state labor force statistics could be greater in states 

with more unauthorized residents or higher 

underrepresentation, especially if, for example, the 

unemployment rate of unauthorized residents who are not 

represented in CPS data differs from estimates for the rest of 

the state population.

Finding 3: Possible Effects (cont.)

Page 35 GAO-10-99 U.S. Labor Force Statistics
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29

Implications

• Although the overall unemployment rate appears not to be sensitive to 

possible underrepresentation of unauthorized residents, other labor force 

statistics (such as the size of the labor force) could be. Therefore:

• Fuller representation of unauthorized residents in the CPS and other 

surveys would improve the accuracy of some labor force statistics. 

• Fuller representation might be especially important in states with 

high concentrations of unauthorized residents, where 

underrepresentation may produce pronounced effects on labor force 

statistics.1

• In general, better information about the unauthorized population would 

help policymakers implement laws and evaluate policies that apply 

differently to foreign-born persons who reside here legally and to 

unauthorized residents. We are continuing to monitor federal efforts 

related to possible approaches for evaluating representation of the 

foreign-born population in data collected. 

1The same may be true for certain occupational categories, industrial sectors, or local areas, but examinations of 

the effects for these groups are beyond the scope of this briefing.

Page 36 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

30

• For our March 2008 detailed simulations, we used publicly available CPS 

estimates of the U.S. unemployment rate, size of the labor force, and 

number of employed persons aged 16 and older.1

• March 2008 was the most recent time for which we were able to obtain 

published estimates of the number of unauthorized residents in the 

labor force (Passel and Cohn, 2009(a)).

• We also used Jeffrey S. Passel’s unpublished estimate that 7.2 million 

unauthorized residents aged 16 and older in the U.S. labor force were 

represented in the March 2008 CPS.2

• Passel made this estimate before he adjusted CPS data for 

underrepresentation.

• While we did not vary this figure in our simulations, we performed 

sensitivity analyses and determined that our findings would not change 

if we increased or decreased Passel’s figure by up to 20 percent.

Appendix A

Methods for Simulating National Labor Force 

Statistics

1CPS data, which we and Passel used as starting points in our analyses, are weighted to reflect the Census Bureau’s 

national population estimates and to correct for survey nonresponse.

2Passel estimated the March 2008 labor force participation rate of represented unauthorized residents to be 76.5 percent.

Page 37 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

31

• We initially simulated national labor force statistics using a range of 

assumptions based on the opinions of one government and three 

private sector experts, who suggested that 

• the underrepresentation of unauthorized residents in CPS data 

might be between 10 and 15 percent and 

• unemployment among unauthorized residents, as of March 2008, might range from 6.5 to 8.5 percent.1

• Using these values, we simulated revised versions of

• the national unemployment rate, 

• the number of persons in the U.S. labor force, and 

• the number employed in the United States.

• To test whether more extreme assumptions would change our 

results, we also calculated additional simulated values for March 

2008 using values of 0 to 50 percent for both underrepresentation 

and the unemployment rate of unauthorized residents.

Methods for Simulating National Labor Force 

Statistics (cont.)

Appendix A

1For example, if 7.2 million of the unauthorized resident labor force are represented in the CPS but 10 percent of this population are not represented, 

the total numbers 8 million, with 800,000 not represented. If the 800,000 have an unemployment rate of 8 percent, 64,000 are unemployed. To 

recalculate the existing unemployment rate, we add 64,000 to its numerator (number unemployed) and 800,000 to its denominator (total in labor force).

Page 38 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

32

We examined whether the resulting simulated labor force statistics fell 

within the margins of error for reported BLS statistics.1

Table 1: March 2008 Labor Force Statistics and Margins of Error 

(Civilian Noninstitutional Population Aged 16 and Older)

Statistic CPS Estimate Lower 90% 

Confidence Interval

Upper 90% 

Confidence Interval 

Unemployment 

Rate 5.24% 5.08% 5.41%

Labor Force 153,135,000 152,629,000 153,641,000

Employed 

Persons 145,108,000 144,567,000 145,649,000

Methods for Simulating National Labor Force 

Statistics (cont.)

Source: Calculated by GAO using published CPS data. 

1 The margins of error correspond to 90 percent confidence intervals around the reported statistics. We use labor 

force statistics that are not seasonally adjusted.

Appendix A

Page 39 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

33

• To determine whether our results would likely be similar under more 

recent economic conditions, we updated our analysis using June 

2009 CPS data on the unemployment rate (8.7%), labor force (155 

million), and employed persons(141 million). 

• We assumed that the number of unauthorized residents in the labor 

force represented in the CPS was unchanged from March 2008 (7.2 

million).

• We used the same broad range of assumptions for 

underrepresentation (0 to 50 percent) and unemployment rate (0 to 

50 percent) and compared the results with the 90 percent 

confidence interval for the June 2009 statistics. 

Methods for Simulating National Labor Force 

Statistics (cont.)

Appendix A

Page 40 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

34

• While this study focused on possible underrepresentation of one 

specific group, unauthorized residents, it is also possible that CPS 

data under- or overrepresent the general population by a small 

amount (based on factors such as net undercounting and 

overcounting in the 2000 census).1

• Our simulations did not adjust for any overall under or 

overrepresentation in the CPS, but we tested our results to 

determine whether they would be affected by an overall error of 

less than one-half of 1 percent in either direction.

• This sensitivity analysis showed that adjusting for a small overall 

error would not substantially change our results.

Methods for Simulating National Labor Force 

Statistics (cont.)

1 For more information on possible overall counting error in the 2000 census, see Mary Mulry, “Summary of 

Accuracy and Coverage Evaluation for Census 2000,” Research Report Series, Statistics #2006-3 (Washington, 

D.C.: U.S. Census Bureau, Feb. 28, 2006). 

Appendix A

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Appendix I: Briefing Slides 

35

Data Sources for Labor Force Statistics We 

Examined

• The Current Population Survey (CPS), which is the primary data 

source for the statistics examined here, is a nationally representative 

monthly survey of approximately 60,000 households administered by 

the Census Bureau. 

• BLS uses CPS data to calculate statistics such as 

unemployment rates, the size of the labor force, and the number 

of employed persons. 

• The decennial census (which is not a survey, but a comprehensive 

household-based count) and the American Community Survey 

(ACS) are not used directly in calculating official labor force statistics. 

• The Census Bureau uses them in calculating the national 

population estimates, which are used to weight CPS data.1

• None of these data sources collects information on legal status.

Appendix B

1See appendix C.

Page 42 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

36

Data Sources for Labor Force Statistics We Did 

Not Examine

• The Current Employment Statistics survey is a monthly survey of 

approximately 400,000 employers. The results are used in 

calculating the number of nonfarm jobs, known as payroll 

employment. Those surveyed are drawn from businesses making 

unemployment insurance payments. 

• This survey does not collect data on legal status.

• Unemployment Insurance claims data are collected by states and 

used by BLS as supplementary information in calculating some state 

and local labor force statistics. 

• Unemployment insurance claims data may exclude most 

unauthorized residents, who are ineligible to collect 

unemployment benefits.

Appendix B

Page 43 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

37

CPS Data, National Population Estimates, and 

Underrepresentation

• The Census Bureau weights CPS data to make them consistent 

with national population estimates. 

• The Census Bureau produces the national population estimates (1)

using counts from the decennial census and (2) updating these counts 

based on birth and death records as well as data on net migration from 

the ACS, a large survey that it conducts every year.1

• According to the Census Bureau, the purpose of weighting CPS data 

is to improve accuracy and help minimize underrepresentation.2

• CPS data distributions—such as Hispanics in defined age 

groups—thus match the distributions from the national population 

estimates. However, problems affecting the national population 

estimates logically “carry over” to the weighted CPS data, 

including any underrepresentation of unauthorized residents.

Appendix C

1 For more information on national population estimates, see U.S. Bureau of the Census, Methodology for the United States Resident Population Estimates by 

Age, Sex, Race, and Hispanic Origin (Vintage 2008): April 1, 2000, to July 1, 2008, http://www.census.gov/popest/topics/methodology/2008-nat-meth.pdf. 2U.S. Census Bureau, Current Population Survey: Design and Methodology, Technical Paper 66, October 2006. See chapter 10, especially the section on 

national coverage adjustment.

Page 44 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

38

CPS Data, National Population Estimates, and 

Underrepresentation (cont.)

• National population estimates may underrepresent a group 

if, for example, that group is undercounted in the census or 

partially composed of foreign-born residents who may be 

underrepresented in the ACS.

• Undercounting in the decennial census is thought to be 

higher for unauthorized residents than for others. 

• Undercounting in the decennial census occurs when a household is

missed or an individual is omitted from the list of persons residing in a 

covered household.1

• To illustrate, if a subpopulation (such as the unauthorized population) 

numbers 12 million and the census fails to count 1.2 million of them, 

the undercount would be 1.2 million or 10 percent.

Appendix C

1For a discussion of undercoverage and related issues, see Groves et al., Survey Methodology, 2nd Edition 

(Hoboken, N.J.: John Wiley & Sons, Inc., 2009). 

Page 45 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

39

CPS Data, National Population Estimates, and 

Underrepresentation (cont.) 

• While the Census Bureau uses census data and the national 

population estimates to improve the accuracy of CPS data, it does 

not make statistical adjustments to correct for undercounting in the 

census or underrepresentation in the national population estimates.

• Regarding the issue of statistical adjustment of the census,1 a topic 

of discussion among policymakers over the years, the director of the 

Census Bureau said in a May 15, 2009, testimony before the Senate 

Committee on Homeland Security and Governmental Affairs:

“I agree fully...that statistical adjustment of the census is eliminated 

as an option for reapportionment...[or] redistricting. The 2003 

decision of [the then Census Bureau] director...assured that no 

implementation infrastructure for adjustment was put in place for 

[the] 2010 [census].”

Appendix C

1The U.S. Supreme Court ruled in 1999 that the use of statistical sampling was statutorily prohibited for purposes 

of apportioning seats in the House of Representatives, but did not specifically address its use for other purposes. 

Dep’t of Commerce v. U.S. House of Representatives, 525 U.S. 316 (1999).

Page 46 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

40

CPS Data, National Population Estimates, and 

Underrepresentation (cont.)

Underrepresentation of unauthorized residents in CPS data may be

caused by factors additional to undercounting in the census, including 

• possible underrepresentation of unauthorized residents in the 

ACS or miscategorization of some members of key groups 

(e.g., Hispanics)—which would affect how CPS data are 

weighted, and

• nonresponse in the CPS, which occurs, for example, when no 

one in a selected household is available to take the survey.1

Appendix C

1To correct CPS data for nonresponse, the Census Bureau increases the weights of the answers of respondents 

who might be similar to nonrespondents, but this may not fully address nonresponse on the part of unauthorized 

residents.

Page 47 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

41

Grouped Answers Approach to Estimating the 

Unauthorized Resident Population

• The "grouped answers" approach is a questionnaire method that 

might be used in private-sector, personal-interview surveys to 

obtain information about the overall population of unauthorized 

residents, while ensuring the anonymity of individual survey 

responses.1

• This personal-interview approach 

• shows each respondent a flash card with answers grouped 

in three boxes, 

• asks the respondent to "just pick the box" that contains his 

or her current legal status (along with other statuses), and 

thus

• avoids questioning respondents about whether they are 

unauthorized. 

Appendix D

1See GAO, Estimating the Undocumented Population: A “Grouped Answers” Approach to Surveying ForeignBorn Respondents, GAO-06-775 (Washington, D.C.: Sept. 29, 2006). 

Page 48 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

42

Grouped Answers Approach to Estimating the 

Unauthorized Resident Population (cont.)

• Estimation for an overall population is possible because the 

grouped answers approach (two card version)

• divides respondents into two subsamples; 

• shows subsamples 1 and 2 slightly different cards (see the 

following slide);1 and 

• compares the percentages that picked key boxes, as 

indicated by the arrow on the following slide.

• When the grouped answers approach is applied in a personal 

interview survey conducted by a university or private-sector 

organization, it appears to be acceptable to foreign-born 

respondents and, with certain provisions, to immigrant 

advocates. 

Appendix D

1No one is asked to respond to both cards. This method (1) has thus far not been developed for mail surveys and 

(2) is not appropriate for telephone interviewing because respondents must view the flash cards.

Page 49 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

43

Figure 3: Legal Status Cards 1 and 2 Compared

Appendix D

Page 50 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

44

List of Experts Consulted

• Experts who suggested parameters for our simulations:1

• Steven A. Camarota, Center for Immigration Studies

• Randy Capps, Migration Policy Institute

• Michael D. Hoefer, U.S. Department of Homeland Security

• Jeffrey S. Passel, Pew Hispanic Center

• Experts who reviewed our work:

• Douglas S. Massey, Office of Population Research, Princeton 

University

• Fritz J. Scheuren, National Opinion Research Center, 

University of Chicago 

• Robert E. Warren, former Director, U.S. Immigration Statistics 

Division, Immigration and Naturalization Service

Appendix E

1We chose these four experts on the basis of their recent experience in estimating the unauthorized population. 

Camarota, Hoefer, and Passel suggested possible underrepresentation levels, and Camarota, Capps, and 

Passel commented on unemployment levels.

Page 51 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

45

Selected References

• Camarota, Steven A. and Karen Jensenius. “A Shifting Tide: 

Recent Trends in the Illegal Immigrant Population.” Washington, 

D.C.: Center for Immigration Studies, July 2009.

• Groves, Robert M. et al. Survey Methodology, 2nd edition. Hoboken, 

N.J.: John Wiley & Sons, Inc, 2009.

• Hoefer, Michael, Nancy Rytina, and Bryan C. Baker. “Estimates of 

the Unauthorized Immigrant Population Residing in the United 

States: January 2008.” Office of Immigration Statistics, U.S. 

Department of Homeland Security. 

• Marcelli, Enrico A. and Paul M. Ong. “Estimating the Sources of the 

2000 Census Undercount among Foreign-born Mexicans in Los 

Angeles County.” Prepared for the Annual Population Association 

of America Meetings. Atlanta, Georgia: May 10, 2002.

Page 52 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

46

Selected References (cont.)

• Mulry, Mary. “Summary of Accuracy and Coverage Evaluation for Census 

2000.” Research Report Series, Statistics #2006-3. Washington, D.C.: U.S. 

Census Bureau, Feb. 28, 2006.

• Passel, Jeffrey S. and D’Vera Cohn. “A Portrait of Unauthorized Immigrants 

in the United States.” Washington, D.C.: Pew Hispanic Center, April 14, 

2009 (a).

• Passel, Jeffrey S. and D’Vera Cohn, “Mexican Immigrants: How Many 

Come? How Many Leave?” Washington, D.C.: Pew Hispanic Center, July 

22, 2009 (b).

• Slater, Courtenay M. “The Impact of Census Undercoverage on Federal 

Programs.” Conference on Census Undercount: Proceedings of the 1980 

Conference. Washington, D.C.: U.S. Bureau of the Census, July 1980. 

Pages 107-111.

• U.S. Census Bureau. Current Population Survey: Design and Methodology. 

Technical Paper 66. Washington, D.C.: October 2006. 

Page 53 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

47

GAO Contacts: 

Nancy Kingsbury, Managing Director, Applied Research and 

Methods, (202) 512-2700, kingsburyn@gao.gov

Cornelia M. Ashby, Director, Education, Workforce, and Income 

Security, (202) 512-7215, ashbyc@gao.gov

Staff Acknowledgments: 

Gale C. Harris and Judith A. Droitcour, Assistant Directors; Brittni 

Milam, Analyst-in-Charge; and Susan Aschoff, Eric M. Larson, 

Rhiannon Patterson, Meredith Trauner, and Monique B. Williams 

made significant contributions to this report. 

GAO Contacts and Staff Acknowledgments

Page 54 GAO-10-99 U.S. Labor Force Statistics
Appendix I: Briefing Slides 

48

• Estimating the Undocumented Population: A “Grouped Answers”

Approach to Surveying Foreign-Born Respondents. GAO-06-775. 

Washington, D.C.: September 29, 2006. 

• Illegal Alien Schoolchildren: Issues in Estimating State-by-State 

Costs. GAO-04-733. Washington, D.C.: June 21, 2004. 

• Overstay Tracking: A Key Component of Homeland Security and a 

Layered Defense. GAO-04-82. Washington, D.C.: May 21, 2004. 

• Survey Methodology: An Innovative Technique for Estimating 

Sensitive Survey Items. GAO/GGD-00-30. Washington, D.C.: 

November 1999.

• Immigration Statistics: Information Gaps, Quality Issues Limit Utility 

of Federal Data to Policymakers. GAO/GGD-98-164. Washington, 

D.C.: July 31, 1998. 

Related GAO Reports 

Page 55 GAO-10-99 U.S. Labor Force Statistics
Appendix II: Comments from the Department Appendix II: Comments from the Department of Commerce 

of Commerce 

Page 56 GAO-10-99 U.S. Labor Force Statistics
Appendix II: Comments from the Department 

of Commerce 

Page 57 GAO-10-99 U.S. Labor Force Statistics
Appendix II: Comments from the Department 

of Commerce 

(130898) Page 58 GAO-10-99 U.S. Labor Force Statistics
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