CONGRESS OF THE UNITED STATES

CONGRESSIONAL BUDGET OFFICE

A

PAPER

CBO

Projections of Net Migration

to the United States

JUNE 2006

A Series on Immigration
Pub. No. 2774
The Congress of the United States O Congressional Budget Office

CBO

Projections of Net Migration

to the United States

June 2006

A

PAPER

Preface

Estimates of the medium- and long-term outlook for the economy and the federal budget depend greatly on projections of the size and composition of the nation’s population. One 

element of such projections is predicting the net flows of immigrants from abroad—an exercise subject to considerable uncertainty.

This paper, requested by the Chairman and Ranking Member of the Senate Finance Committee, is one of several reports by the Congressional Budget Office (CBO) that present facts and 

research on immigration to help inform the agency’s projections of the economy and the federal budget. The paper examines projections of net migration. In keeping with CBO’s mandate to provide objective, nonpartisan analysis, the paper makes no recommendations.

David A. Brauer wrote the paper under the supervision of Douglas Hamilton. Andrew 

Gisselquist provided research assistance. The paper benefited from the comments of Bob 

Dennis, Douglas Hamilton, Arlene Holen, Kim Kowalewski, Noah Meyerson, John Peterson, 

John Sabelhaus, Jonathan Schwabish, Michael Simpson, Bob Shackleton, Ralph Smith, and 

Julie Topoleski. Harriet Orcutt Duleep of the Urban Institute and Felicitie C. Bell of the 

Office of the Chief Actuary of the Social Security Administration also provided helpful comments. (The assistance of such external participants implies no responsibility for the final 

product, which rests solely with CBO.)

John Skeen edited the paper, and Christine Bogusz proofread it. Maureen Costantino prepared the paper for publication, and Lenny Skutnik produced the printed copies.

Donald B. Marron

Acting Director

June 2006

Contents

Summary 1

The Social Security Trustees’ Projections 2

The Census Bureau’s Projections 3

Issues Raised by the 2003 Social Security Technical Panel 6

Other Analyses of Future Immigration 8

Conclusions 10

Table

1. Projections of Net Migration in Selected Years 3

Figures

1. The Social Security Trustees’ and Technical Panel’s 

Projections of Net Migration 4

2. The Census Bureau’s Projections of Net Migration 5

3. The Number of Immigrants Admitted by Fiscal Year 7

4. Alternative Projections of Net Migration Rates 8

Projections of Net Migration

to the United States

Summary

Estimates of the medium- and long-term economic and 

budget outlook rely on projections of the size and composition of the nation’s population. One challenge to 

such projections is forecasting how many immigrants will 

come to and stay in the United States. Because most

immigrants are of working age when they arrive, rates of 

net migration are critical in determining the growth of 

the labor force.1 Indeed, over the past decade, foreignborn workers accounted for more than half of the growth 

of the labor force.2 Moreover, the composition of the immigrant population could also make a difference to the 

outlook.

Two federal entities—the Social Security trustees, within 

the Social Security Administration, and the Census 

Bureau—currently generate projections of net migration as a component of their population projections. The 

Congressional Budget Office (CBO) does not independently project either net migration or the size and composition of the population, instead relying on those agencies’ expertise and access to detailed information. In 

particular, both CBO’s 10-year projections of the growth 

of the labor force and its long-term projections for Social 

Security are based on the trustees’ population projections, 

which incorporate their assumptions regarding net migration. 

Immigration projections are subject to a large degree of 

uncertainty even in the near term. In fact, the two agencies’ projections for net migration in 2010 range, under 

plausible alternative assumptions, from as low as 150,000 

to more than 1.5 million people. Analysis of historical 

data implies an 80 percent probability that over the next 

decade, net migration will average between about 

500,000 and 1.5 million people annually, with the range 

of possible outcomes narrowing somewhat over a longer 

horizon.3

This paper examines the projection methodologies and 

outlines the most recent projections of the Social Security 

trustees and the Census Bureau.4

 The trustees’ projections are higher than those of the Census Bureau in the 

near term but lower after 2025. 

The paper then addresses issues about those projections 

raised by the 2003 Technical Panel on Assumptions and 

Methods. In the panel’s view, both the trustees’ and the 

Census Bureau’s projections underestimate future net migration. The Social Security trustees and the Census Bureau, along with CBO, are currently evaluating the technical panel’s recommendations. 

Finally, the paper discusses factors that might influence 

the level and composition of net migration. In principle, 

one might be able to improve on current projections by 

explicitly modeling key determinants of both the poten1. In this paper, net migration over any specified time period refers 

to the number of people legally admitted to the United States as 

permanent residents, refugees, or people seeking asylum minus the 

number of legal permanent residents who emigrate, plus the net 

increase or decrease in the number of unauthorized residents. People admitted as temporary residents—for example, as students or 

under the Department of State’s H1 program—are not included. 

However, the projections do take into account the likelihood that 

some people initially admitted as temporary residents will subsequently become legal permanent residents.

2. See Congressional Budget Office, The Role of Immigrants in the 

U.S. Labor Market (November 2005).

3. See Congressional Budget Office, Quantifying Uncertainty in the 

Analysis of Long-Term Social Security Projections (November 2005).

4. The projections discussed in this paper reflect, to varying degrees, 

current laws and policies.
2 PROJECTIONS OF NET MIGRATION TO THE UNITED STATES

tial supply of immigrants and the potential demand for 

immigrant workers. Those theoretical insights may be 

helpful in assessing broad trends, though at present they 

appear to be of limited value for quantitative projections. 

The Social Security Trustees’

Projections

The Social Security trustees’ projections for immigration 

are relatively straightforward. Their “intermediate” projection, which is presented as the most likely outcome, 

has total net migration at 1.075 million in 2005 and 

2006, declining to 1 million annually beginning in 2007, 

950,000 per year starting in 2016, and 900,000 per year 

in 2026 and thereafter.5 Those projections incorporate 

separate assumptions for legal immigration, emigration of 

legal foreign-born residents, and net “other” migration. 

The latter category comprises unauthorized residents as 

well as individuals who are legally admitted but not seeking permanent residence. 

Under current law, the trustees are required to prepare 

projections of the financial solvency of the Social Security 

system. In those projections, the system’s revenues 

depend on income from wages, salaries, and selfemployment, which are affected by the size and composition of the working-age population. Program costs depend on the size and composition of the beneficiary population and its members’ earnings history.6 From the 

agency’s perspective, higher rates of immigration improve 

the system’s solvency, at least for a time—because the immigrant population is disproportionately composed of 

people of prime working ages, with relatively small percentages of children and the elderly. However, outlays are 

also affected: those immigrants will eventually retire and 

become eligible to collect Social Security benefits. 

The trustees’ general approach in projecting the size and 

composition of the population is to move from recently 

established trends toward long-range ultimate values over 

a period of five to 25 years. In the case of immigration, 

those ultimate values are expressed as an average annual 

net number of immigrants. 

The trustees’ projections for net legal immigration of 

600,000 people beginning in 2007 are based on the assumption that current policies will continue. The Immigration Act of 1990 calls for a “flexible cap” of 675,000 

immigrant admissions per year; consequently, the projections assume that, on average, that many people will be 

admitted as legal permanent residents each year beginning in 2007.7

 In addition, the projections include 

125,000 people admitted annually as refugees or people 

seeking asylum or under other miscellaneous categories. 

The latter figure reflects annual ceilings for admissions of 

refugees, which averaged about 120,000 during the mid1990s, plus actual recent admissions of asylum-seekers 

and others.8 The trustees also assume a rate of emigration 

averaging 25 percent of the level of legal immigration (including by refugees and asylum-seekers), a level consistent with the best available estimates of emigration rates 

among the foreign-born population.9

 The trustees’ projections assume that net “other” (primarily unauthorized) 

immigration remains at its estimated current level of 

400,000 annually through 2015, dropping to 350,000 by 

2016 and to its ultimate level of 300,000 by 2026. The 

lower ultimate level corresponds to mid-1990s estimates 

of unauthorized migration between 1988 and 1992.10

The trustees recognize that projections of immigration 

are subject to considerable uncertainty and therefore 

present both “low-cost” and “high-cost” variants. The 

“low-cost” variant is associated with a higher rate of net 

migration (because immigration boosts the number of 

5. Social Security Administration, The 2006 Annual Report of the 

Board of Trustees of the Federal Old-Age and Survivors Insurance and 

Federal Disability Insurance Trust Funds (May 1, 2006).

6. The level of an individual worker’s retirement benefits under 

Social Security is based on his or her average level of annual earnings, adjusted for the growth of average earnings throughout the 

economy. A spouse of that worker is eligible for an amount equal 

to 50 percent of the benefits (100 percent if widowed) or a larger 

amount based on his or her own earnings history.

7. For a description of current policies regarding immigration, see 

Congressional Budget Office, Immigration Policy in the United 

States (February 2006).

8. However, since 2002 the ceiling on admissions of refugees has 

declined to 70,000 per year, and only about 10,000 people were 

granted asylum in 2003 and 2004. 

9. Tammany J. Mulder, Betsy Guzman, and Angela Brittingham, 

Evaluating Components of International Migration: Foreign-Born 

Emigration, Working Paper No. 62 (Washington, D.C.: U.S. 

Census Bureau, Population Division, April 2002). 

10. See Felicitie C. Bell, Social Security Area Population Projections: 

1997, Actuarial Study No. 112 (Social Security Administration, 

August 1997), available at www.ssa.gov/OACT/NOTES/

s1990s.html.
PROJECTIONS OF NET MIGRATION TO THE UNITED STATES 3

Table 1.

Projections of Net Migration in Selected Years

(Thousands of people per year)

Source: Congressional Budget Office based on Social Security Administration, The 2006 Annual Report of the Board of Trustees of the 

Federal Old-Age and Survivors Insurance and Federal Disability Insurance Trust Funds (May 1, 2006), available at www.ssa.gov/

OACT/TR/TR06; Frederick W. Hollmann, Tammany J. Mulder, and Jeffrey E. Kallan, Methodology and Assumptions for the 

Population Projections of the United States: 1999 to 2100, Working Paper No. 38 (Washington, D.C.: U.S. Census Bureau, Population 

Division, January 2000), available at www.census.gov/population/www/documentation/twps0038.html; U.S. Census Bureau, 

National Population Projections, Summary Files, “Components of Change for the Total Resident Population: Middle Series, 1999 to 

2100” (January 2000), Table NP-T6, available at www.census.gov/population/www/projections/natsum-T6.html; and U.S. Census 

Bureau, Interim Projections of the U.S. Population by Age, Sex, Race, and Hispanic Origin: Summary Methodology and Assumptions

(March 2004), available at www.census.gov/ipc/www/usinterimproj/idbsummeth.html.

a. The Census Bureau’s interim projection is an update of its middle-series projection.

workers paying taxes into the Social Security system more 

than it boosts the number of beneficiaries receiving payments); conversely, the “high-cost” variant is associated 

with a lower rate of net migration. Thus, while the trustees’ intermediate projection assumes total net migration 

of 1.075 million people in 2006 and 900,000 per year in 

2026 and beyond, the alternative variants yield a range 

from 810,000 to 1.27 million in 2006 and from 672,500 

to 1.3 million per year ultimately (see Table 1 and 

Figure 1). Specifically, the “low-cost” scenario has net legal immigration rising from 720,000 in 2006 to its ultimate level of 850,000 in 2007, with net other migration 

of 550,000 annually between 2006 and 2015, falling to 

its ultimate level of 450,000 in 2026; those figures are 

slightly above recent estimated levels of net migration, 

but the ultimate projected level of net migration is below 

the trustees’ estimated post-World War II peak that occurred in 2001 (excluding the effects of the Immigration 

Reform and Control Act of 1986, which temporarily 

raised the number of legal immigrants during the late 

1980s and early 1990s).11 By contrast, the “high-cost” 

scenario calls for net legal immigration of 560,000 people 

in 2006, dropping to its ultimate level of 472,500 in 

2007. In that scenario, net other immigration is assumed 

to be just 250,000 in 2006, with an ultimate level of 

200,000 in 2016. 

The Census Bureau’s Projections 

The Census Bureau’s forecast is considerably more detailed and disaggregated than that of the Social Security 

trustees but is based on older data. The Census Bureau’s 

most recent complete set of forecasts was issued in 2000, 

with an interim update in 2004 (whereas the trustees’ 

most recent forecast was prepared and issued in 2006). 

The bureau forecasts the numbers for various categories 

of migrants (including immediate relatives, refugees, unauthorized immigrants, and so forth) separately and estimates the number of “in-migrants” and “out-migrants” 

separately. 

The number of out-migrants is specifically modeled as a 

function of the size and characteristics of the foreign-born

 2006 2010 2015 2020 2025 2030 2050 2100

Social Security Administration (2006)

“Low cost” 1,270 1,400 1,400 1,350 1,350 1,300 1,300 1,300

Intermediate 1,075 1,000 1,000 950 950 900 900 900

“High cost” 810 723 723 673 673 673 673 673

U.S. Census Bureau (2000)

High series 1,645 1,571 1,726 1,854 2,269 2,680 2,814 3,047

Interim projection (2004)a 920 766 796 819 996 1,161 1,097 1,058

Middle series 872 713 734 751 912 1,061 984 926

Low series 317 149 130 120 182 233 166 113

11. Social Security Administration, The 2006 Annual Report of the 

Board of Trustees.
4 PROJECTIONS OF NET MIGRATION TO THE UNITED STATES

Figure 1.

The Social Security Trustees’ and Technical Panel’s Projections of Net Migration

(Thousands of people)

Source: Congressional Budget Office based on Social Security Administration, The 2006 Annual Report of the Board of Trustees of the Federal Old-Age and Survivors Insurance and Federal Disability Insurance Trust Funds (May 1, 2006), available at www.ssa.gov/OACT/

TR/TR06; and 2003 Technical Panel on Assumptions and Methods, Report to the Social Security Advisory Board (October 2003),

available at www.ssab.gov/documents/2003TechnicalPanelRept_000.pdf.

Notes: The historical figures are estimated. The trustees’ projections of immigration are components of their assessment of the fiscal

solvency of the Social Security system.

As discussed in the text, the 2003 Technical Panel on Assumptions and Methods, appointed by the Social Security Advisory Board,

offered an alternative projection to the trustees’ intermediate projection.

population.12 Like the trustees, the Census Bureau has issued alternative projections with higher and lower rates of 

immigration than in its baseline “middle series.” 

The middle-series projection assumes that total net migration was 964,000 in 2000 and that it will fall to 

872,000 in 2005 and 713,000 in 2010 and rise to a peak 

of about 1.1 million in 2030 (see Table 1 and Figure 2). 

Subsequently, net migration would decline, reflecting an 

assumed constant level of immigration but a rising level 

of emigration.

The middle-series projection for the near term is based 

largely on established trends in migration to the United 

States from various parts of the world and an assessment 

as to whether those trends are likely to continue. That 

projection assumes that the total number of immigrant 

visas available in numerically limited categories will remain unchanged until 2020 but allows for variation in 

other categories of legal immigration. The projection for 

total immigration reflects several other key assumptions. 

Legal immigration from Mexico and Central America increased sharply during the 1990s; Census Bureau analysts 

attributed much of that increase to the Immigration

1990 2000 2010 2020 2030 2040 2050 2060 2070

0

500

1,000

1,500

2,000

2,500

3,000

"Low Cost" Technical Panel

Intermediate

"High Cost"

Historical Projected

12. The Census Bureau’s projections also take net migration between 

the United States and Puerto Rico into account, whereas the trustees’ do not (because Puerto Rico is within the Social Security 

area). In addition, the Census Bureau’s projections allow for the 

emigration of native-born people, while the trustees’ do not.
PROJECTIONS OF NET MIGRATION TO THE UNITED STATES 5

Figure 2.

The Census Bureau’s Projections of Net Migration

(Thousands of people)

Source: Congressional Budget Office based on U.S. Census Bureau, National Population Projections, Summary Files, “Components of 

Change for the Total Resident Population: Middle Series, 1999 to 2100” (January 2000), Table NP-T6, available at www.census.gov/

population/www/projections/natsum-T6.html; and U.S. Census Bureau, Interim Projections of the U.S. Population by Age, Sex, 

Race, and Hispanic Origin: Summary Methodology and Assumptions (March 2004), available at www.census.gov/ipc/www/

usinterimproj/idbsummeth.html.

Note: The historical figures are estimated. 

Reform and Control Act of 1986, which legalized the 

presence of many previously unauthorized residents and 

made them eligible to eventually attain citizenship.13

Once naturalized, they could sponsor the legal immigration of immediate relatives, which is not subject to numerical limits, thereby temporarily boosting net migration. However, immigration from that source was 

thought to have peaked early in this decade and assumed 

to gradually decline to zero. Consequently, legal immigration from Mexico was assumed to return to its level of the 

early 1990s by 2010. Inflows of refugees were also expected to decline, primarily resulting from fewer applications from the former Yugoslavia. In the bureau’s projections, other legal immigration was predicted to follow 

established trends, with adjustments for the perceived 

“supply” of potential immigrants in source countries. 

Emigration of legal foreign-born residents was subsequently projected on the basis of historical estimates of 

rates taking age, sex, and country of birth into account, 

multiplied by the size of the “at-risk” population.14

However, in light of evidence that most emigrants are 

people who have arrived in the United States recently, the 

bureau is currently reviewing its procedures for projecting 

emigration. 

1990 2000 2010 2020 2030 2040 2050 2060 2070

0

500

1,000

1,500

2,000

2,500

3,000

High Series

Low Series

Middle Series

Interim Projection

Historical Projected

13. Frederick W. Hollmann, Tammany J. Mulder, and Jeffrey E. 

Kallan, Methodology and Assumptions for the Population Projections 

of the United States: 1999 to 2100, Working Paper No. 38 

(Washington, D.C.: U.S. Census Bureau, Population Division, 

January 2000).

14. Those estimates were derived by comparing the number of 

foreign-born people enumerated in the 1980 census with the 

number enumerated in the 1990 census who had arrived before 

1980, with adjustments for deaths and for estimated differences in 

the degree of underreporting between the two censuses. 
6 PROJECTIONS OF NET MIGRATION TO THE UNITED STATES

For the longer term (after 2020), the Census Bureau’s 

projections show rising immigration. In the middle series, 

the annual level of immigration rises from 1.09 million in 

2020 to 1.45 million in 2030, then remains at that level 

until 2100. That jump reflects the projected rapid increase in the dependency ratio (the number of children 

and elderly people relative to the size of the working-age 

population) in the United States and resulting faster 

growth in the demand for labor relative to its domestic 

supply. The underlying notion is that the surge in labor 

demand will lead to a greater inflow of immigrants, either 

by inducing less-restrictive policies toward immigration 

or by raising wages so that migration to the United States 

(legal or otherwise) becomes more attractive. Thus, although the Census Bureau’s projections are consistent 

with current law through 2020, that assumption is not 

necessarily maintained for subsequent years. Net migration levels decline after 2030, reflecting the assumption 

of a constant level of immigration while emigration 

continues to rise because of a still-growing “at-risk” 

population.

The Census Bureau notes that the actual level of immigration will ultimately depend on factors such as policy 

decisions; external economic and political conditions; 

and, in the long run, demographic developments in 

source countries. To convey the degree of uncertainty surrounding projections of immigration, the bureau also 

presents high and low variants. In developing the alternative projections, the bureau assumed that the spread between variants would widen over time.15 As a result,

the Census Bureau’s highest and lowest projections encompass a much wider range of possible outcomes than 

the Social Security trustees’ “low-cost” and “high-cost” 

variants.

Since its 2000 forecast, which was prepared before the results of the 2000 census were known, the bureau has issued an “interim” forecast, which adjusts its estimates of 

the immigrant population using information from the 

2000 census and incorporates a slightly higher probability that the high-immigration scenario in its previous 

forecast will occur.16 According to those results, the actual resident population of the United States on April 1, 

2000, was 281.4 million, significantly higher than the 

figure of 274.5 million that had been estimated for that 

date on the basis of the 1990 census; most of the difference is attributable to higher-than-anticipated net migration during the 1990s.17 The interim projection implies 

net migration of 920,000 in 2005.18 Compared with the 

trustees’ intermediate projection, both the Census Bureau’s middle series and its interim projection show moderately lower net migration over the next two decades but 

moderately higher net migration after 2025.

Issues Raised by the 2003 Social 

Security Technical Panel 

The 2003 Technical Panel on Assumptions and Methods 

was appointed by the Social Security Advisory Board to 

review the trustees’ methodology and key demographic 

and economic assumptions used to project the future financial status of the system’s trust funds, including assumptions about immigration. The panel’s report specifically addressed the trustees’ immigration projections, but 

the issues raised by the panel apply more generally.19

Broadly speaking, the panel identified three questions 

that it judged to be fundamental to projecting migration. 

First, should the forecasts be based on levels of migration 

(the number of people migrating each year) or derived as 

percentages of some population? The latter would imply 

rising levels simply resulting from the growth in the underlying population. Second, to what extent and on what 

basis should the projections be allowed to deviate from 

established historical trends? Third, to what extent 

should the projections be based on current laws and 

policies? 

15. Emigration acts to slightly dampen the deviations between the 

Census Bureau’s alternative scenarios. Out-migration rates are 

higher in the low-migration series and lower in the high-migration 

series, but because the population at risk of emigrating is potentially much larger in the high series than in the middle or low 

series, the total number of emigrants is larger in the high series. 

16. The probability reflects a weighted average of.938 times the 2000 

middle series and .062 times the high series.

17. The population projections issued in early 2000 assumed a

foreign-born population of 26.8 million in July 2000; the actual 

foreign-born population enumerated in the 2000 census was 31.1 

million.

18. The bureau recently estimated that net migration was about 1.05 

million between July 2004 and July 2005 and has averaged 1.2 

million annually since the 2000 census. Those estimates, however, 

are not reflected in the bureau’s near-term projections (to 2020). 

19. See 2003 Technical Panel on Assumptions and Methods, Report to 

the Social Security Advisory Board (October 2003), available at 

www.ssab.gov/documents/2003TechnicalPanelRept_000.pdf.
PROJECTIONS OF NET MIGRATION TO THE UNITED STATES 7

Figure 3.

The Number of Immigrants Admitted by Fiscal Year

(Thousands of people)

Source: Congressional Budget Office based on Department of Homeland Security, Office of Immigration Statistics, 2004 Yearbook of

Immigration Statistics (2004), Table 4 (Immigrants), available at www.uscis.gov/graphics/shared/statistics/yearbook.

a. Refers to people already living in the United States when admitted as legal permanent residents.

The panel recommended that assumptions about net migration be based on an analysis of historical trends, not 

on current laws or policies. It noted that only one component of the trustees’ projections—legal admissions excluding refugees and asylum-seekers—is based on current 

law. And even that flexible cap of 675,000 admissions 

does not apply to the largest single category of legal immigrants: immediate relatives of U.S. citizens. For that 

group, there is no numerical restriction on the number of 

people admitted. Moreover, the number of people actually admitted has exhibited significant variability from 

year to year, and many of those admitted had already arrived in the United States in an earlier year (see Figure 3). 

In assessing historical trends, the panel pointed to a number of factors that might influence the volume of immigration to the United States in the near term. Some of 

those factors would tend to boost the number of immigrants relative to recent trends. For example, the demand 

for immigrant labor is likely to climb along with growth 

in the U.S. population and economy, particularly as 

members of the baby-boom generation begin to retire. 

Other factors might dampen immigration. For instance, 

heightened security concerns following the September 11 

terrorist attacks might slow the process of admitting immigrants and refugees and lead to increased border enforcement. Nonetheless, the panel noted that the average 

growth of the annual net inflow had been about 4 percent 

since 1950 and concluded that, on balance, there was

no strong reason to anticipate a break in that trend. The 

continuation of that rising trend is at odds with the trustees’ and Census Bureau’s projections, both of which assume a roughly constant level of net migration in the near 

term.20

1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

0

500

1,000

1,500

2,000

Total

Adjustment

of Status

New Arrivals

a

20. The panel admitted to some uncertainty as to what the appropriate starting point should be. It adopted the trustees’ estimated net 

number of about 1.2 million migrants in 2002—the last full year 

for which data were available at the time of the panel’s report. 

However, the trustees’ latest projections, issued in May 2006, start 

from a lower base of an estimated 1.075 million migrants in 2005.
8 PROJECTIONS OF NET MIGRATION TO THE UNITED STATES

Figure 4.

Alternative Projections of Net Migration Rates

(Migrants per thousand people of the U.S. population)

Source: Congressional Budget Office based on Social Security Administration, The 2006 Annual Report of the Board of Trustees of the Federal Old-Age and Survivors Insurance and Federal Disability Insurance Trust Funds (May 1, 2006), available at www.ssa.gov/OACT/

TR/TR06; 2003 Technical Panel on Assumptions and Methods, Report to the Social Security Advisory Board (October 2003), available at www.ssab.gov/documents/2003TechnicalPanelRept_000.pdf; U.S. Census Bureau, National Population Projections, Summary Files, “Components of Change for the Total Resident Population: Middle Series, 1999 to 2100” (January 2000), Table NP-T6, 

and “Annual Projections of the Total Resident Population as of July 1: Middle, Lowest, Highest, and Zero International Migration 

Series, 1999 to 2100,” Table NP-T1, available at www.census.gov/population/www/projections.

The panel recommended that the long-run projections 

for net migration should be expressed not as a level, but 

rather as a rate—the annual net number of migrants divided by the size of the population. That rate had risen 

from a very low level in the 1940s and 1950s to around 4 

per thousand in recent years—roughly comparable to the 

average rate during the previous period of high net inflows of immigrants between 1840 and 1910. The panel 

suggested that the rate be assumed to gradually decline to 

its historical (1821-2002) average of 3.2 per thousand 

(see Figure 4). But with the population continuing to 

grow, that assumption would still yield a steady increase 

in the net number of immigrants, which would reach 

about 1.4 million by 2080 (see Figure 1 on page 4). For a 

“low-cost” variant, the panel suggested a net migration 

rate held constant at its 2002 level of 4.15 per thousand, 

resulting in a net migration level of close to 2.1 million 

annually by 2080 and to 2.3 million annually by 2100. 

The panel viewed the trustees’ assumption for its middle 

series of a constant net number of migrants as appropriate 

in a “high-cost” scenario. 

Other Analyses of Future Immigration

Some experts take an approach to forecasting immigration that differs from that of the technical panel. For example, Lee, Miller, and Anderson use a statistical timeseries model to assess alternative net immigration projections and conclude that the preferred projection model 

should be based on the level of immigration rather than 

on its rate.21 The authors base their analysis on data from 

1925 through 2002—a period in which the average im2005 2015 2025 2035 2045 2055 2065 2075

0.0

1.5

2.0

2.5

3.0

3.5

4.0

Technical Panel (2003)

Census Bureau's Middle Series (2000)

Trustees' Intermediate (2006)

21. Ronald Lee, Timothy Miller, and Michael Anderson, Stochastic 

Infinite Horizon Forecasts for Social Security and Related Studies, 

Working Paper No. 10917 (Cambridge, Mass.: National Bureau 

of Economic Research, November 2004).
PROJECTIONS OF NET MIGRATION TO THE UNITED STATES 9

migration rate was below that of the 1821-2002 period 

cited by the technical panel. They chose 1925 as their 

starting point because it represents the first full year following the adoption of the restrictive Federal Immigration Act of 1924; immigration patterns before that year, 

the authors argue, are irrelevant for purposes of projecting into the 21st century. In their model, the projected 

net number of immigrants (legal and illegal) falls from 

the estimated 2002 level of 1.2 million to about 1 million 

in 2020, then slowly rises back to about 1.2 million. 

Those projections are generally higher than those of the 

Social Security trustees and the Census Bureau but below 

those of the technical panel. 

Beyond methods that generally extend either levels or 

trends, it may be possible to improve projections by explicitly taking into account factors that are believed to influence rates of immigration. Indeed, there are numerous 

potential influences on the number of immigrants to the 

United States, although how those factors will play out 

and in some cases interact may in practice be quite difficult to predict. 

A recent analysis by Howe and Jackson lays out a number 

of broad theoretical frameworks that could help to assess 

both “push” factors—factors influencing the potential 

supply of immigrants to the United States and other 

countries—and “pull” factors—factors influencing the 

attractiveness of the United States and other countries as 

a destination for immigrants.22 Push factors typically refer to conditions in potential source countries, such as

demographics, wages and employment opportunities, 

and the degree of political freedom. Pull factors include 

wages and employment opportunities in the United 

States, the presence of an existing community of earlier 

immigrants, and policies that either promote or inhibit 

immigration.23

One framework for analysis focuses on how policies toward migration influence behavior. For example, some 

analysts operating within that framework have concluded 

that tighter border enforcement can at least for a time 

paradoxically boost net unauthorized migration. Members of a large unauthorized population already present in 

the United States are deterred from returning to their 

home country for fear that they will be unable to reenter, 

and that effect outweighs the direct effect on entry. However, a key insight is that in the long run, policy and enforcement are influenced by underlying social, economic, 

and demographic trends.

Economic analysis of migration patterns emphasizes the 

function of an increasingly global labor market. In that 

view, people will choose to migrate from low-wage to 

high-wage countries if and to the extent that higher earnings are expected to compensate for the costs of moving. 

That framework takes into account both push and pull 

factors and lends itself well to quantitative projections. 

Migration to the United States will be positively correlated with wage growth and perceived employment opportunities here and negatively correlated with the pace 

of economic development in source countries and with 

the expected costs and risks of moving. 

A limitation of traditional economic analysis, at least according to some analysts, is that it ignores the roles of culture and social ties (except to the extent that they are implicitly included in estimates of moving costs). Other 

theories attempt to incorporate such factors—as exemplified by one that gauges societies’ integration into the global economy. Immigrants typically come not from the 

poorest societies, but rather from those that have already 

been integrated to some degree into the global market 

economy. Once that integration occurs, migration begins 

as people recognize that they can improve their standard 

of living. As the first wave of immigrants sends remittances home, the standard of living of remaining family 

members rises, but at the same time so do their aspirations for further gains, thus leading to additional waves of 

immigrants.24 The supply of potential immigrants will 

then depend in part on the rate at which the remaining 

traditional societies are integrated into the global

economy.

Another approach emphasizes the role of family subgroups, treating migration as reflecting a series of decisions made within the family over a period of a number 

of years. Migration not only generates income in the 

form of remittances but also offers diversification of in22. Neil Howe and Richard Jackson, Long-Term Immigration Projection Methods: Current Practice and How to Improve It, Working 

Paper No. 2006-3 (Boston, Mass.: Boston College, Center for 

Retirement Research, February 2006).

23. For more information on the determinants of migration, see 

Congressional Budget Office, Global Population Aging in the 21st 

Century and its Economic Implications (December 2005).

24. For a discussion of remittances, see Congressional Budget Office, 

Remittances: International Payments by Migrants (May 2005).
10 PROJECTIONS OF NET MIGRATION TO THE UNITED STATES

come sources. Over time, family subgroups move back 

and forth between the sending and receiving communities. Wage differentials between the source and receiving 

countries continue to play a role, but that role is secondary to the objective of reducing the uncertainty of income. Moreover, the family and community linkages that 

arise as people from a particular source community migrate to a particular receiving community serve to reduce 

the risks and moving costs associated with migration. 

Such analysis implies that migration patterns are likely to 

persist for some time even if the original precipitating factors are no longer present.

Several other factors are likely to affect future immigration patterns. One is fertility in key source countries. 

According to data from the 2000 census, about 30 percent of the foreign-born population came from Mexico. 

However, the fertility rate in Mexico, which stood at 6.8 

children per woman in 1970, had fallen to 2.4 per 

woman by 2000 and is expected to continue declining.25

Consequently, the population of potential immigrants is 

currently growing at a much slower rate than in the recent past, which could slow the growth of migration from 

Mexico. In addition to economic and demographic factors, potential immigration to the United States from any 

source country depends on political factors, including 

freedom and stability as well as policies regarding the ease 

of emigration. And an array of noneconomic and economic factors could influence the perceived attractiveness 

of the United States as a destination for immigrants relative to alternative destinations (such as Canada, Europe, 

Japan, and Australia). 

Conclusions

Immigration projections are subject to a high degree of 

uncertainty. Predicting future levels of net migration requires assumptions not only about whether immigration 

will rise or fall relative to its current level but also about 

what that current level is. Unfortunately, that level—particularly its unauthorized component—can be estimated 

only imprecisely. The Census Bureau’s projections, at 

least in the near term, reflect estimates of recent net migration levels that appear to be too low. The Social 

Security trustees’ projections, on which CBO’s 10-year 

projections for the labor force are based, are more consistent with recent estimated levels of net migration. However, the trustees’ assumption that net unauthorized migration will decline from estimated recent levels can be 

questioned.

There is no consensus among experts regarding the issues 

raised by the Social Security Technical Panel, particularly 

whether to project net migration using levels or rates. For 

preparing a projection of the most likely scenario, it is 

probably reasonable to deviate from an assumption that 

extends current laws and policies, particularly over longer 

time horizons. If that assumption about current laws and 

policies is required for analytical reasons, it need be 

applied only to numerically limited categories. For other 

categories of legal immigration—by immediate relatives 

of U.S. citizens, refugees, and asylum-seekers, for instance—projections can be based on historical trends and 

averages and on an assessment of the potential inflows of 

such immigrants. 

The most important source of uncertainty will be in projecting unauthorized migration. Here, it would be appropriate to begin with historical trends, adjusting them 

where possible on the basis of an assessment of the various push and pull factors. But such an exercise would 

probably be difficult, both because many of the factors 

are themselves difficult to predict and because there may 

be complex interactions among them. Finally, although 

the theoretical framework is useful in highlighting factors 

that can influence the rate of net migration, it offers little 

guidance as to how quantitatively important any of the 

effects are. 

25. Jeffrey S. Passel, “Unauthorized Migrants: Numbers and Characteristics” (background briefing prepared for the Task Force on 

Immigration and America’s Future, June 2005).