US Undocumented Population Increased to 11.7 Million in July 2023: Provisional CMS Estimates Derived from CPS Data
Robert Warren
September 5, 2024
Introduction
The sharp rise in arrivals and enforcement activities at the southern border over the past few years has focused attention on undocumented migration and added extra urgency to questions about the size and growth of the undocumented population in the United States. These questions have social, humanitarian, economic, and political implications.
In the 1980s, speculative estimates of the size of the population were often in the 10 to 12 million range (Corwin, 1982). The exaggerated inflation of those numbers was exposed with the passage of the Immigration Reform and Control Act of 1987 (IRCA). A total of 3 million applied for legalization. Unfounded speculation about the size of the population has returned. An article in The Hill [1] in January 2024 asserted that the population has grown by 10 million over the past three years based primarily on tallies of DHS enforcement actions. As in the 1980s, attempted entries were confused with population growth. This report includes a section that explains why the number of DHS ”encounters” and estimated “gotaways” has always greatly exceeded undocumented population growth. The estimates for 2023 presented here are based on rigorous demographic analysis of survey data that have been adjusted for undercount. The methodology is described in a later section.
The estimates are based on data collected by two Census Bureau surveys, the American Community Survey (ACS) and the Current Population Survey (CPS). The ACS is an annual survey covering approximately one percent of the total US population. The CPS is a much smaller monthly survey of about 60,000. The CPS collects detailed demographic data, but its main emphasis is on labor force data.
The best data for determining the size of the undocumented population comes from the ACS,[2] though estimates based on that survey are usually about two years behind. Given the importance of an accurate and up-to-date estimate, particularly when national attention is focused on it, CMS has produced this research note, which shows a provisional [3] estimate for 2023 based on the CMS estimate of the undocumented population in 2022 and data from the 2022 and 2023 CPS. If the estimation procedure described here produces information consistent with 2023 estimates derived from more reliable ACS data, the Center for Migration Studies will publish estimates for 2024 later this year.
Total Undocumented Population In 2023
The total undocumented population increased to about 11.7 million in July 2023, an increase of about 800,000 compared to the previous July (Figure 1). The estimate for 2023 is below the peak of 12 million reached in 2008. After 2008, the population steadily declined, falling to 10 million in 2020. Population growth in 2022-2023 was about 200,000 less than the previous high of one million in 2000-2001 (Figure 2).
Source: Center for Migration Studies. (Click the image to expand)
Source: 1990 to 2009, Warren and Warren 2013; 2010 to 2023, CMS. (Click the image to expand)
Figure 3 shows trends in the undocumented population from 2017 to 2023 for Mexico and for three geographic areas. The relatively small size of the Current Population Survey compared to the American Community Survey limits the geographic detail available for 2023. The estimates for 2017 to 2022 in Figure 3 are from the CMS publication series, and the figures for 2023 are the provisional estimates described here.
(Click the image to expand)
In the 6-year period illustrated in Figure 3, the undocumented population from Mexico declined about 630,000, and the population from “All other” countries increased by 160,000. Most of the undocumented population growth from 2017 to 2023 was from Central America (1,120,000) and South America (445,000).
Methodology
The estimates for 2023 shown in this report are based on data collected in the CPS and estimates of undocumented residents derived by CMS. We used the relationship between CMS estimates of undocumented residents and CPS data for 2022 to project the size of the population in 2023. The relatively small sample size of the CPS limited the geographic detail of the 2023 estimates to Mexico, Central America, Caribbean, South America, Europe, “Korea, Philippines and Vietnam combined,” and “All other countries.”
The data in Table 1 illustrate the procedures used to estimate the undocumented population from Mexico in 2023 based on 2023 CPS data. The ratio of the CMS estimate for 2022 to CPS data for 2022 (Step 3 below) was multiplied by CPS data for 2023 to estimate the undocumented population from Mexico in July 2023 (Step 5).
We tested the methodology by constructing CPS-based projections for 2018 to 2022 and comparing the results to estimates CMS published for those years. The methodology described here generated estimates within a range of +/- 200,000, or 2 percent of the CMS estimates (Table 2).
When the CMS estimates for 2023, derived from ACS data, become available at the end of this year, the estimate could be slightly higher or lower than the estimated total of 11.7 million shown here for 2023. If the methodology described here produces an estimate for 2023 that is close to the final CMS ACS-based estimate for 2023, we intend to use March 2024 CPS data to publish an estimate of the total undocumented population for 2024 before the end of this year.
Why Apprehensions Do Not Represent Undocumented Population Growth
DHS has apprehended millions of migrants attempting to cross the southern border without inspection over the past few years. The question could be asked: How could the total undocumented population increase by “only” 800,000 from 2022 to 2023?
This section lists many reasons why apprehensions do not equal undocumented population growth. One important reason is that the US Border Patrol is more effective than many media accounts indicate. In 2021, DHS estimated that it interdicted 80.9 percent of attempted entries. [4]
Other reasons why apprehensions do not equal population growth: some are apprehended a second or third time, some are trying to return to a residence in the United States after a visit abroad, some are seasonal workers, some are coming temporarily to visit family, and many are bona fide asylum applicants. None of these instances add to the undocumented population residing in the United States.
Taking a broad historical perspective, we can compare undocumented population growth and total DHS apprehensions from 1990 to 2019. The population increased by 6.8 million, and there were 33.7 million [5] apprehensions over the 30-year period. On average, the population grew by 1 person for every 5 apprehensions.
Arrivals of undocumented immigrants are offset by many hundreds of thousands of departures from the undocumented population each year, including those that emigrate voluntarily, are removed by DHS, adjust to legal status, or die. Reliable statistics are not available to measure these four ways of leaving the undocumented population. However, data are available to determine the number of foreign-born persons that emigrate or die, as described next.
From 2010 to 2022, the total foreign-born population counted in the ACS increased by just 6 million, from 40 million to 46 million. Over that 12-year period, 13.1 million were admitted by DHS for lawful permanent residence, the number of temporary residents (students, workers, their families, and others) increased by .9 million, and an estimated 6.0 million undocumented immigrants arrived. A total of 20 million arrived, yet the population increased by just 6 million. That means 14 million – nearly 1.2 million per year – emigrated or died over the 12-year period.
Summary
As described in the previous section, apprehensions greatly exceed undocumented population growth because the US Border Patrol is more effective than is often reported, some attempting entry are apprehended multiple times, many who are apprehended and released into the United States will be granted asylum, hundreds of thousands adjust status to lawful permanent residence each year or are removed by DHS. More than a million foreign-born persons leave the country each year.
The most reliable estimates of the undocumented population are derived from detailed statistics collected in the ACS. Even though the results are adjusted for undercount, it is possible that undercount has increased with the larger inflow of undocumented residents. In that case, the estimates described here would be higher by the amount of the additional undercount. On the other hand, the estimates include a large number of noncitizens – likely well over a million – that are not immediately deportable but are not authorized to remain here permanently. The latter group includes DACA recipients, those with TPS (Temporary Protected Status), and asylum applicants that eventually will be granted legal permanent resident status.
The large speculative numbers described at the beginning of this report are exciting, and they receive a lot of media attention, but in every case so far, the “estimates” have proved to be woefully inadequate. Any current estimate that is outside a range of about 11 to 13 million should be greeted with skepticism, and those who make such claims should disclose details of their data and methodology.
The estimates shown in Figure 1 indicate that the long-term decline of the undocumented population – from 12 million in 2008 to about 10 million in 2020 – has ended, at least for a few years. The provisional estimate of 11.7 million for 2023 is still below the historic peak of 12 million reached in 2008. The population grew by about 800,000 from 2022 to 2023, about 200,000 below undocumented population growth in 2000-2001, as shown in Figure 2.
The estimates for 2023 shown here are based on a new technique that will be tested with the release of 2023 ACS data later this year. If the estimation procedure described here produces information consistent with 2023 estimates derived from more reliable ACS data, the Center for Migration Studies will continue to derive and publish 1-year projections based on CPS data.
References
Arthur F. Corwin, The Numbers Game: Estimates of Illegal Aliens in the United States, 1970–1981, 45 Law and Contemporary Problems 223-297 (Spring 1982)
Available at: https://scholarship.law.duke.edu/lcp/vol45/iss2/11
Steven Ruggles, Sarah Flood, Matthew Sobek, Daniel Backman, Annie Chen, Grace Cooper, Stephanie Richards, Renae Rodgers, and Megan Schouweiler. IPUMS USA: Version 15.0 [dataset]. Minneapolis, MN: IPUMS, 2024. https://doi.org/10.18128/D010.V15.0
Warren, R. (2024). After a Decade of Decline, the US Undocumented Population Increased by 650,000 in 2022. Journal on Migration and Human Security, 12(2), 85-95. https://doi.org/10.1177/23315024241226624
R. Warren, J. R. Warren, Unauthorized Immigration to the United States: Annual Estimates and Components of Change, by State, 1990 to 2010. International Migration Review 47, 296–329 (2013).
[1] https://thehill.com/opinion/4423296-matthews-illegal-immigrants-double-under-biden-and-thats-just-the-start/
[2] The most recent CMS estimates of the undocumented population were for July 2022. The estimates, including a description of the methodology CMS used, were published in January 2024 (Warren 2024).
[3] We refer to these estimates as provisional because the methodology has not been used before. The estimate of the total population shown here will be compared to the estimate for 2023 derived from ACS data. The 2023 estimates based on ACS data and 2024 estimates derived from CPS data should be available by the end of this year.
[4] Source: Table 1, https://www.dhs.gov/sites/default/files/2023-07/2023_0703_plcy_fiscal_year_2022_border_security_metrics_report_2021_data.pdf
[5] Source of population data: Same as for Figure 2; apprehension data from 2019 DHS Yearbook of Immigration Statistics, Table 33.
September 6, 2024