Updated: 2025-08-21
The number of undocumented immigrants living in the United States is a subject of ongoing debate, with estimates varying significantly depending on the methodology used and the source conducting the research.
According to the most recent data from the Pew Research Center, approximately 14 million unauthorized immigrants lived in the United States as of 2023, marking a record high [1]. This represents an increase from previous years, with Pew estimating 11 million in 2019 and 10.5 million in 2021 [1]. The 2023 figure constitutes about 4.2% of the total U.S. population [1].
The Department of Homeland Security provides similar estimates, calculating approximately 11 million unauthorized immigrants as of January 2022 [2]. Other organizations like the Center for Migration Studies estimate the number at around 11.7 million as of July 2023 [3].
Some researchers argue that traditional estimation methods significantly undercount the actual unauthorized population. A 2018 study from MIT Sloan used mathematical modeling based on operational data and suggested the true number could be roughly double the conventional estimates, potentially ranging from 16.2 to 29.5 million, with a mean estimate of 22.1 million [4]. These researchers argued that traditional survey-based methods may miss significant portions of this population due to inherent limitations in data collection [4].
It’s crucial to distinguish between different immigration-related statistics that are sometimes conflated:
The variation in estimates stems from different methodological approaches. Most mainstream estimates rely on the “residual method,” which compares census data on foreign-born residents with administrative data on legal immigration [1][2]. Critics of this approach argue it may undercount individuals who avoid government surveys or live in hard-to-reach communities [4].
The most widely accepted current estimate is between 11-14 million unauthorized immigrants living in the United States, though some researchers suggest the actual number could be significantly higher.
[1] Pew Research Center - Reports a record 14 million unauthorized immigrants in 2023, representing the highest level recorded, based on analysis of government data using the residual method.
[2] FactCheck.org - Provides context on various immigration statistics, distinguishing between border encounters and the resident unauthorized population, citing DHS estimates of 11 million.
[3] BBC News - Reports on various estimates of the unauthorized immigrant population, including data from the Center for Migration Studies.
[4] MIT Sloan - Presents research suggesting the unauthorized population could be roughly double conventional estimates, potentially 22.1 million, based on mathematical modeling.
[5] House Homeland Security Committee - Focuses on border encounter statistics rather than the resident population, reporting nearly 3 million inadmissible encounters in FY2024.
Short answer
Why the numbers differ
Bottom line
Sources 1) Pew Research Center (records a higher, latest estimate). Record 14 million unauthorized immigrants lived in the U.S. in 2023; indicates growth to a record level by 2023. https://www.pewresearch.org/race-and-ethnicity/2025/08/21/u-s-unauthorized-immigrant-population-reached-a-record-14-million-in-2023/
2) FactCheck.org (explains definitions and cautions against misusing “encounters”). Breaks down immigration figures; notes earlier mainstream estimates around 10–11 million and emphasizes that border encounters and “gotaways” cannot be equated to the resident unauthorized population. https://www.factcheck.org/2024/02/breaking-down-the-immigration-figures/
3) BBC News (reflects mainstream, lower recent-range context). Explains how many migrants are in the U.S. and what happens to them; cites commonly used estimates near 11 million and discusses measurement caveats. https://www.bbc.com/news/articles/c0jp4xqx2z3o
4) U.S. House Committee on Homeland Security (flow statistics, not a population estimate). Fact sheet noting nearly 3 million encounters in FY2024 and about 10.8 million since FY2021; useful for understanding border activity, but not a measure of the unauthorized population living in the U.S. https://homeland.house.gov/2024/10/24/startling-stats-factsheet-fiscal-year-2024-ends-with-nearly-3-million-inadmissible-encounters-10-8-million-total-encounters-since-fy2021/
5) MIT Sloan article on a 2018 study (outlier, much higher estimate). Summarizes research estimating the undocumented population could be roughly double conventional estimates (mean ~22 million in 2016), a finding that is disputed by many demographers. https://mitsloan.mit.edu/ideas-made-to-matter/study-undocumented-immigrant-population-roughly-double-current-estimate
There is no single, universally agreed-upon figure for the number of immigrants living illegally in the United States. Estimates vary significantly depending on the methodology, data sources, and the time period being analyzed. The most credible analyses place the number anywhere from just over 10 million to over 20 million people.
Historically, the most widely cited estimates have placed the unauthorized immigrant population at around 11 million. The Department of Homeland Security estimated the population at 11 million in 2018, while the Pew Research Center placed it at 10.5 million in 2021 [2, 4]. These figures are typically calculated using the “residual method,” which involves subtracting the number of legal foreign-born residents from the total foreign-born population captured in census data [4].
However, due to an increase in border crossings since 2021, most analysts agree that this population has grown. Reflecting this trend, some recent estimates are significantly higher:
A 2018 study from researchers at the MIT Sloan School of Management and the Yale School of Management produced a dramatically higher estimate. Using a mathematical model based on operational data—such as deportations, visa overstays, and mortality rates—rather than census surveys, the researchers concluded that the undocumented immigrant population was 22.1 million in 2016 [1]. This figure is roughly double the conventional estimates from the same period, and while it represents a different academic perspective, it is not as widely cited as the lower figures from organizations like the Pew Research Center [1, 4].
It is important to distinguish between the total population of unauthorized immigrants living in the U.S. (a “stock”) and the number of border “encounters” (a “flow”). Government data often highlights the number of encounters, which are events, not unique individuals [2].
For example, the House Committee on Homeland Security reported nearly 3 million “inadmissible encounters” at the U.S. border in Fiscal Year 2024 and a total of 10.8 million encounters since the start of Fiscal Year 2021 [3]. However, these numbers include individuals who may have been stopped multiple times, as well as those who were immediately expelled and never entered the U.S. interior [2]. Therefore, encounter figures reflect the scale of attempted crossings but do not directly translate to the net increase in the number of unauthorized immigrants residing in the country [2, 3].
Error: Grok API error: 429
The number of unauthorized immigrants living in the United States is estimated to be between 10.5 and 12 million people as of recent estimates, though precise figures are inherently difficult to determine due to the population’s undocumented nature.
According to the Department of Homeland Security (DHS), there were approximately 11 million unauthorized immigrants residing in the United States as of January 2022 [1]. This represents a slight increase from their 2020 estimate of 10.5 million [1]. The Pew Research Center, using different methodology, estimated the unauthorized immigrant population at 10.5 million in 2021, down from a peak of 12.2 million in 2007 [2].
The Migration Policy Institute (MPI) provides similar estimates, calculating approximately 11 million unauthorized immigrants as of 2021 [3]. These organizations use different methodological approaches but arrive at broadly similar figures, suggesting the estimates are relatively reliable within a margin of error.
The unauthorized immigrant population grew rapidly from the 1990s through 2007, when it reached its historical peak [2]. Since then, the numbers have remained relatively stable or slightly declined. The Great Recession of 2008-2009, increased border enforcement, and changing migration patterns from Mexico have all contributed to this stabilization [2][3].
The largest share of unauthorized immigrants comes from Mexico, though this proportion has decreased over time. As of 2021, Mexicans made up about 37% of the unauthorized population, down from 57% in 2007 [2]. Other significant origin countries include El Salvador, Guatemala, Honduras, China, and India [3].
Geographically, unauthorized immigrants are concentrated in several states. California, Texas, Florida, New York, New Jersey, and Illinois account for the majority of this population [1][3]. About two-thirds of unauthorized immigrants have lived in the United States for more than 10 years [2].
Estimating the unauthorized immigrant population involves significant challenges. Researchers typically use a “residual method,” which compares the total foreign-born population (from Census data) with the legally present foreign-born population (from administrative records) [1][2]. The difference provides an estimate of the unauthorized population, though this method has inherent limitations and margins of error.
Unauthorized immigrants comprise approximately 4.6% of the U.S. civilian workforce, despite representing about 3.3% of the total U.S. population [2]. They are particularly concentrated in industries such as construction, agriculture, hospitality, and domestic services [3].
[1] Department of Homeland Security Office of Homeland Security Statistics - “Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2020-2022” - Provides official government estimates using administrative and survey data. https://www.dhs.gov/ohss/topics/immigration/unauthorized-immigrants
[2] Pew Research Center - “Key facts about U.S. immigration policies and Biden’s proposed changes” - Offers comprehensive demographic analysis and historical trends of unauthorized immigration using Census data and residual methodology. https://www.pewresearch.org/fact-tank/2022/01/11/key-facts-about-u-s-immigration-policies-and-bidens-proposed-changes/
[3] Migration Policy Institute - “Profile of the Unauthorized Population: United States” - Provides detailed demographic breakdowns and state-level analysis of the unauthorized immigrant population. https://www.migrationpolicy.org/data/unauthorized-immigrant-population/state/US
Short answer: The best available, nonpartisan estimates indicate that roughly 10.5–11 million unauthorized (undocumented) immigrants are living in the United States. Pew Research Center estimates 10.5 million in 2021, while the Center for Migration Studies estimates about 10.6 million in 2022. Both note the total remains below the 2007 peak of about 12.2 million, with modest growth since the late 2010s [1][2].
What that means and why estimates vary
Trends to know
Bottom line: A reasonable, evidence-based statement is that about 11 million people are living in the U.S. without lawful immigration status, with most rigorous estimates landing between 10.5 and 11 million in 2021–2022 and suggesting modest growth since then [1][2][3].
Sources 1) Pew Research Center (Passel, Cohn, et al.). Uses survey-based residual methods; estimates 10.5 million unauthorized immigrants in 2021; notes the 2007 peak (~12.2 million) and subsequent decline, with stabilization in 2021. https://www.pewresearch.org/short-reads/2023/11/13/us-unauthorized-immigrant-population-size-stabilized-in-2021-after-a-decade-of-change/
2) Center for Migration Studies (Robert Warren; CMS Data Hub). Residual-method estimates placing the unauthorized population at about 10.6 million in 2022, up modestly from 2019 but below earlier peaks. https://data.cmsny.org/
3) Congressional Budget Office (CBO). Nonpartisan macro-demographic analyses that place the unauthorized population at roughly 11 million in 2021 and discuss factors likely increasing the foreign-born population in 2022–2024; cautions about data lags and measurement. https://www.cbo.gov/ (see CBO primers and immigration briefs; figure frequently cited as “about 11 million”)
4) Pew Research Center (Fact Tank explainer on methods). Explains how and why estimates of the unauthorized population are produced and why some methods yield higher (contested) numbers. https://www.pewresearch.org/short-reads/2018/09/21/what-we-know-about-unauthorized-immigrant-population-estimates/
5) Yale/MIT (Fazel-Zarandi, Feinstein, Kaplan, 2018; PLOS ONE). Outlier estimate suggesting 16.7–22.1 million for 2010–2016 using a different demographic model; widely debated and critiqued by mainstream demographers. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0201193
6) Federation for American Immigration Reform (FAIR). Advocacy organization reporting substantially higher figures (e.g., ~16.8 million in 2022) based on assumptions of large survey undercounts; not a consensus estimate among population researchers. https://www.fairus.org/issue/illegal-immigration/how-many-illegal-aliens-united-states
Estimating the number of immigrants in the United States without legal authorization is a complex task, as there is no official government census of this population. Instead, government agencies, think tanks, and academic institutions produce estimates based on demographic and statistical analysis. Consequently, different sources provide slightly different numbers, but they generally fall within a specific range.
The most widely cited estimates for the unauthorized immigrant population in recent years place the figure between 10.3 million and 11 million. However, these figures are typically based on data from 2021 or 2022. More recent analyses suggest a significant increase in this population since then due to a rise in net immigration.
Pew Research Center: A leading source for this data, the Pew Research Center estimated that there were 10.5 million unauthorized immigrants in the U.S. in 2021. This number was largely unchanged from 2019 and represented a decline from a peak of 12.2 million in 2007. The population had remained relatively stable for over a decade prior to recent increases in border arrivals [1].
U.S. Department of Homeland Security (DHS): The most recent official government estimate comes from the DHS, which reported that 11.0 million unauthorized immigrants were living in the U.S. as of January 1, 2022. This figure marked a slight increase from the 10.5 million estimated in 2020 [2].
Center for Migration Studies (CMS): CMS, a non-partisan think tank, estimated the unauthorized population to be 10.38 million at the end of 2022. Their analysis noted that while arrivals have increased, the total population number has been moderated by other factors, such as departures, deaths, and adjustments of legal status [3].
These estimates are generally calculated using the “residual method.” Researchers take the total number of foreign-born individuals living in the U.S. from surveys like the U.S. Census Bureau’s American Community Survey (ACS) and subtract the number of legally resident foreign-born individuals. The remaining “residual” number is the estimated unauthorized population. This method has limitations, including potential undercounts in surveys and reliance on demographic assumptions.
Since the data for the estimates above were collected (mostly in 2021 and 2022), there has been a significant increase in migrant encounters at the U.S. southern border. This has led many analysts to conclude that the total unauthorized population has grown.
The terminology used to describe this population is often a subject of debate.
In summary, while the most established, peer-reviewed estimates place the unauthorized immigrant population at around 10.5 to 11 million based on 2021-2022 data, more recent analysis accounting for the surge in migration since then suggests the current number is likely significantly higher, possibly in the range of 12 to 14 million.
Passel, Jeffrey S. and Jens Manuel Krogstad. Pew Research Center. This source provides an estimate of 10.5 million for 2021. The authors are demographers who focus on long-term population trends, noting that the unauthorized population had declined from its 2007 peak and stabilized for over a decade before the recent increase in border arrivals. Key facts about unauthorized immigrants in the U.S.
U.S. Department of Homeland Security (DHS), Office of Immigration Statistics. This is the U.S. government’s official estimate. The report places the unauthorized population at 11.0 million as of January 2022. It uses a standard residual methodology based on Census Bureau data and is considered a baseline figure by many researchers. Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2022
Warren, Robert. Center for Migration Studies (CMS). This report estimates a lower figure of 10.38 million for the end of 2022. The author argues that while new arrivals are high, estimates often do not fully account for emigrations, deportations, and status adjustments, which offset the total population growth. The Number of Undocumented Immigrants in the US Continued to Decline from 2020 to 2022, But the Number of New Arrivals Has Been Increasing
Congressional Budget Office (CBO). This report focuses on the economic and budgetary outlook, but includes projections on net immigration. The CBO expresses the view that net immigration of “other foreign nationals” (a proxy for the unauthorized population and those with temporary statuses) increased dramatically in 2022 and 2023, which implies significant growth in the total unauthorized population since the last formal estimates were produced. The 2024 Long-Term Budget Outlook
Zeigler, Karen and Steven A. Camarota. Center for Immigration Studies (CIS). This organization advocates for lower levels of immigration. Their report presents a significantly higher estimate of 13.7 million as of January 2024. The authors’ view is that the post-2021 increase in border crossings has directly translated into a rapid and substantial expansion of the unauthorized immigrant population, a viewpoint that leads to one of the highest available estimates. The Illegal Immigrant Population of the United States, January 2024
Error: Grok API error: 429