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A Turning Point for the Unauthorized Immigrant Population in the United States
Commentaries
September 2023

A Turning Point for the Unauthorized Immigrant Population in the United States

Vice President Kamala Harris participates in a DACA roundtable
Lawrence Jackson/White House

Approximately 11.2 million unauthorized immigrants lived in the United States in 2021, up from 11.0 million in 2019, according to new Migration Policy Institute (MPI) estimates. This represents larger annual growth in the unauthorized immigrant population than at any point since 2015. While the public, which is regularly exposed to images of chaotic arrivals at the U.S.-Mexico border, might expect an even greater jump in the size of the overall unauthorized immigrant population, it is important to note that these 2021 data do not capture the record number of border encounters witnessed in 2022 and the high levels seen this year.

These estimates also reflect the population as of mid-2021, a period when global mobility was still depressed due to the COVID-19 pandemic. The size of the unauthorized immigrant population is shaped by new entries—border arrivals and visa overstays alike—but also by departures. In 2020, both arrivals and departures seemed to be at lower levels than in previous years.

The observed increase in the size of the unauthorized population between 2019 and 2021 (see Figure 1) is partially explained by increased irregular arrivals at the U.S.-Mexico border. These border arrivals represented a growing mix of nationalities from the Americas and, increasingly, from beyond the hemisphere. The growth also stems from rising numbers of Europeans who overstayed their nonimmigrant visas. Among research organizations that estimate the size of the unauthorized immigrant population, MPI is the first to publish national trends for 2021, using a methodology developed in collaboration with The Pennsylvania State University.

The estimates offered here are based on data from the 2021 American Community Survey (ACS), the latest available from the U.S. Census Bureau. Because the Census Bureau deemed that the 2020 ACS did not meet its quality standards, given the challenges of conducting surveys during the onset of the pandemic, MPI had not generated estimates of the size of the unauthorized immigrant population since the 2019 data became available.

Figure 1. Estimated Size of the Unauthorized Immigrant Population in the United States, 2007-21

Notes: Migration Policy Institute (MPI) estimates of the U.S. unauthorized immigrant population, developed in collaboration with Jennifer Van Hook from The Pennsylvania State University, Population Research Institute, are achieved by subtracting the number of legal immigrants from the total of all immigrants for each country and region represented in U.S. Census Bureau American Community Survey (ACS) data. The number of legal immigrants is estimated by adding up all legal admissions from each country and region in every year—using U.S. Department of Homeland Security (DHS) administrative data—and then reducing this number to account for deaths and emigration of legal immigrants. Finally, the unauthorized immigrant population estimates are adjusted upward slightly to account for the recognized undercount of this population in the ACS. For more detail on this methodology, see MPI, “MPI Methodology for Assigning Legal Status to Noncitizen Respondents in U.S. Census Bureau Survey Data."
Sources: MPI estimates, developed in collaboration with Van Hook. Estimates from other organizations are from Robert Warren, “MPI Methodology In 2019, the US Undocumented Population Continued a Decade-Long Decline and the Foreign-Born Population Neared Zero Growth," Journal on Migration and Human Security 9, no. 1 (March 1, 2021): 31–43; Jeffrey S. Passel and D’Vera Cohn, “Mexicans Decline to Less than Half the U.S. Unauthorized Immigrant Population for the First Time," Pew Research Center, June 12, 2019; Pew Research Center, “Unauthorized Immigrant Population Trends for States, Birth Countries and Regions,” June 12, 2019; Bryan Baker, “Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2015–January 2018,” DHS, Office of Immigration Statistics, January 2021; Bryan Baker, 2018, “Population Estimates: Illegal Alien Population Residing in the United States: January 2015,” DHS, Office of Immigration Statistics, December 2018.

The increase in unauthorized immigrants between 2019 and 2021, which was driven by migration from Central America and Venezuela in particular, was partially offset by emigration of large numbers of Mexican unauthorized immigrants over this period. The Mexican unauthorized immigrant population has been shrinking for more than a decade, falling about 32 percent from its 7.7 million peak just before the 2008-09 Great Recession. MPI estimates that the Mexican unauthorized immigrant population declined by roughly 200,000 people between 2019 and 2021, from 5.4 million to 5.2 million (see Figure 2), likely as a result of repatriations by U.S. immigration authorities as well as voluntary returns to reunite with family, among other factors. It is also likely that as more Mexican migrants are utilizing lawful pathways to come to the United States, including the H-2A visa for seasonal agricultural work, fewer may be inclined to migrate irregularly.

Figure 2. Estimated Size of the Unauthorized Immigrant Population from Mexico in the United States, 2007–21

Sources: MPI estimates, developed in collaboration with Van Hook. Estimates from other organizations are from Warren, “In 2019, the US Undocumented Population Continued a Decade-Long Decline and the Foreign-Born Population Neared Zero Growth;” Passel and Cohn, “Mexicans Decline to Less than Half the U.S. Unauthorized Immigrant Population for the First Time;” Pew Research Center, “Unauthorized Immigrant Population Trends for States, Birth Countries and Regions;” Baker, “Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2015–January 2018;” Baker, “Population Estimates: Illegal Alien Population Residing in the United States: January 2015.”

A Turning Point: Growing Diversification of Origins

While Mexico continued to be the largest origin country of unauthorized immigrants (accounting for 46 percent of the total in 2021, as compared to 63 percent in 2007), declines in the Mexican unauthorized population offset increases in irregular arrivals from other countries. The unauthorized immigrant populations from places such as Guatemala, Honduras, Venezuela, and other parts of South America grew between 2019 and 2021, as did populations from the Caribbean and Africa, among others.

In 2021, the top countries of origin of unauthorized immigrants after Mexico ranged from those in nearby northern Central America to countries such as India, the Philippines, and Colombia (see Table 1).

Table 1. Top 10 Countries of Origin for Unauthorized Immigrants in the United States, 2021

Sources: MPI estimates, developed in collaboration with Van Hook.

Migrants from Latin America and the Caribbean accounted for 79 percent of all unauthorized immigrants in 2021. Eleven percent were from Asia (see Table 2).

Table 2. Regions of Birth of Unauthorized Immigrants in the United States, 2021

Sources: MPI estimates, developed in collaboration with Van Hook.

Why Are the Unauthorized Immigrant Estimates Relatively Stable?

Over the last 15 years, the unauthorized immigrant population has hovered just above or below 11 million, plus or minus a few hundred thousand—with the research organizations that provide such estimates falling within a similar range despite using differing methodologies (see Figure 1).

While this stability seems to defy expectations, given the very high numbers of encounters of unauthorized immigrants by U.S. authorities at the U.S.-Mexico border in recent years, a closer look offers a logical explanation.

The new MPI estimates reflect the population as of mid-2021, the most recent year for which ACS data exist. The post-pandemic rise in migrant encounters at the Southwest border did not start until spring 2021, with peaks occurring in July and August, which are therefore not fully reflected in these estimates. Notably, border encounters in fiscal year (FY) 2022 far exceeded those in FY 2021, and with two months left in the year encounters in FY 2023 already surpassed the total in FY 2021 (see Figure 3).

Figure 3. Migrant Encounters at U.S.-Mexico Border, FY 2019-23

Notes: U.S. Customs and Border Protection (CBP) uses the term “encounters” to account for apprehensions under Title 8 of the U.S. Code and expulsions under the Title 42 public-health order that was implemented from March 2020 to May 12, 2023. Data for fiscal year (FY) 2023 include the period of October 2022 through July 2023.
Sources: MPI tabulations based on data from CBP, “Southwest Border Migration,” updated November 14, 2019, available online; CBP, “Southwest Land Border Encounters,” updated July 18, 2023, available online.

Although the pandemic depressed immigration to the United States, this does not explain why the unauthorized immigrant population has been stable since 2008. One key to understanding this is knowing that, under the surface, the unauthorized immigrant population has never been static. Even as new migrants enter the country, others exit. After spending time living and working in the United States, some people voluntarily leave because they cannot find employment, their money goes further in their communities of origin, they want to be closer to family and friends, or they prefer not to live with the burden of unauthorized status anymore. Still others are deported by immigration authorities (more than 4.7 million removals have been carried out since 2008), with their relatives sometimes electing to rejoin them. Though not easy, other unauthorized immigrants are able to obtain legal status in the United States. Finally, some die.

Beginning in 2008 and continuing through 2021, more Mexican unauthorized migrants have left the United States each year than there have been new unauthorized entrants who are from Mexico, according to the authors’ analysis. Many moved to the United States during the economic boom of the late 1990s and early 2000s to work in construction, agriculture, or service-sector jobs. The 2008-09 recession abruptly reduced job opportunities and many immigrants moved back to Mexico. Additionally, conditions in Mexico had changed. Reductions in family size reduced the pressures on people to work abroad to support their families, and job opportunities started to increase as the Mexican economy recovered from the financial crises of the 1980s and 1990s.

Mexico’s longstanding trend of more migrant departures than arrivals is not replicated by other major sending countries. Among many other unauthorized immigrant groups, new arrivals have outpaced departures, legalizations, deaths, and deportations. Between 2008 and 2021, the unauthorized population from Africa grew by 68 percent; from the Caribbean by 67 percent; from Central America by 52 percent; Asia by 47 percent; Europe, Canada, and Oceania by 32 percent; and South America by 30 percent. But because Mexicans compose nearly half of the overall unauthorized population, their decline has offset increases among all other groups combined.

A Population Likely to Grow Beyond 2021

Trends witnessed since 2021 portend greater shifts in the unauthorized immigrant population into 2023. A combination of the easing of pandemic-era travel restrictions, increasing displacement due to global conflict and climate events, and shifts in regional migration have led to increased migration in the Americas and worldwide. Migration through the Western Hemisphere has become significantly more diverse in nationality, with growing numbers of migrants from far-away countries such as Russia, Turkey, Cameroon, and India arriving at the U.S.-Mexico border.

Multiple factors go into whether the U.S. unauthorized immigrant population has grown since mid-2021. It is possible that the significant rise in migrant arrivals at the Southwest border since 2021—driven by interlocking factors ranging from political repression to strong U.S. labor demand and favorable perceptions of U.S. policy changes—may increase the size of the unauthorized population if large shares stay pending removal or the conclusion of their immigration court proceedings. Visa overstays could also add to this growth if more people remain beyond the duration of their visa, as global travel rebounds. At the same time, emigration could also rise, driven by migrants’ decisions to return home or by stricter enforcement policies, offsetting the increases.

The Growth of a “Twilight” Population

Looking past 2021, another trend that has strongly affected the lives of unauthorized immigrants is that a growing share hold—or even arrive with—some kind of liminal status. MPI has long included in its estimates of the unauthorized population people who hold some sort of twilight status such as Temporary Protected Status (TPS) or Deferred Action for Childhood Arrivals (DACA), which grant the right to work in the United States and protection from deportation but do not offer permanent legal status. MPI estimates also include people in the process of applying for asylum.

While these groups collectively comprised a minority of unauthorized immigrants in 2019 and continue to do so, larger shares of new arrivals are now in some sort of liminal status, with many granted entry with that status. The Biden administration has expanded TPS eligibility to more than 800,000 U.S. residents, including sizable numbers of recent entrants from Haiti, Ukraine, and Afghanistan. Separately, it has allowed entry of hundreds of thousands of migrants from Afghanistan, Cuba, Haiti, Nicaragua, Ukraine, and Venezuela through humanitarian parole, which affords the temporary right to stay and work with authorization. And ever-larger shares of recent border crossers are asylum seekers.

As a result, migrants’ legal status composition in the United States has become more complex. While the term “unauthorized” is an imperfect descriptor for migrants the U.S. government has processed and granted the temporary right to stay, MPI estimates continue to group together these populations given their lack of a visa or other durable legal status.

Future data will reveal how the size and origins of the unauthorized immigrant population have shifted during the very dynamic period of U.S.-Mexico border arrivals in 2022 and 2023. Shifting national origins, protection needs, and migration policies have also changed what the experience of being an unauthorized immigrant in the United States is like—including more with work authorization and a somewhat expanded set of rights but without a fixed immigration status. The 2021 data offered here represent a return to estimates after the pandemic-induced lull.