The unauthorized immigrant population living in the United States has increased from about 8.5 million in 2000 to about 14.7 million in 2024, or by more than 6 million people, with the bulk of that growth occurring after 2020, according to estimates published by research institutes and the U.S. federal government.

The size of the unauthorized immigrant population fluctuated over the 24-year period, with distinct periods of growth, stagnation, and decline (see Figure 1). Contrary to what is commonly assumed, these changes do not necessarily correspond with the political party in the White House. The size of the unauthorized immigrant population rose during the George W. Bush years (+3.3 million), was relatively stable during the Obama years (-0.5 million), declined during the Trump years (-1.0 million), and rose sharply during the Biden years (+4.5 million).

The increase during the Biden administration stands out because it was unusually large. Based on the averages of published estimates, the population increased by roughly 4.5 million between 2020 and 2024, compared with 3.3 million over the eight years of the Bush administration (2.1 million between 2000 and 2004 and 1.2 million between 2004 and 2008).

Estimates for 2024 suggest that the size of the unauthorized immigrant population was about 14.7 million, ranging between about 14 million and 16 million. Historically, estimates from the federal government and nonprofit research organizations have generally tracked and clustered together, despite differences in the organizations’ political leanings. This is not surprising: they broadly use the same residual methodology and draw on the same underlying data (see Additional Information).

More recent estimates suggest the unauthorized immigrant population may have begun to decline. Preliminary monthly estimates from the Center for Immigration Studies show a decline from 15.8 million in January 2025 to 14.2 million in July.

Additional Information

Estimates of the unauthorized population are based on U.S. Census Bureau survey data combined with U.S. Department of Homeland Security administrative records on legally resident immigrants, using residual methods that infer the unauthorized population as a statistical remainder. Differences across sources reflect data vintage and modeling assumptions.

The estimates shown in Figure 1 are the latest historical estimates published by the following organizations: Center for Immigration Studies (CIS), Center for Migration Studies of New York (CMS), Migration Policy Institute (MPI), Pew Research Center (Pew), and the U.S. Department of Homeland Security (DHS). Historical estimates may be revised as underlying population estimates are updated. For additional information on the specific methodologies and data sources used by these organizations, see the citations below.

Center for Immigration Studies

Camarota, Steven A., and Karen Jensenius. “A Shifting Tide: Recent Trends in the Illegal Immigrant Population.” Center for Immigration Studies, July 27, 2009.

Camarota, Steven A., and Karen Zeigler. “Estimating the Illegal Immigrant Population Using the Current Population Survey.” Center for Immigration Studies, March 29, 2022.

Camarota, Steven A., and Karen Zeigler. “Foreign-Born Population Grew by 5.1 Million in the Last Two Years: The Largest Two-Year Increase Ever Recorded.” Center for Immigration Studies, May 13, 2024.

Camarota, Steven A., and Karen Zeigler. “Illegal Population Down Since January: Government data suggests the number of illegal immigrants may have fallen by 1 million.” Center for Immigration Studies, June 19, 2025.

Camarota, Steven A., and Karen Zeigler. “Welfare Use by Immigrants and the U.S.-Born, 2024: Comparing Program Use by Foreign- and U.S.-Born-Headed Households.” Center for Immigration Studies, February 4, 2026.

Center for Migration Studies

Warren, Robert. “Table 1. Estimated Undocumented Population and Components of Change: 1990 to 2017.” Center for Migration Studies of New York, 2019.

Warren, Robert. “US Undocumented Population Continued to Fall from 2016 to 2017 and Visa Overstays Significantly Exceeded Illegal Crossings for the Seventh Consecutive Year.” Journal on Migration and Human Security, February 15, 2019.

Warren, Robert. “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, March 8, 2021.

Warren, Robert. “Undercount of Undocumented Residents in the 2020 American Community Survey and Estimates and Trends in the Undocumented Population from 2010 to 2020, by US State and Country of Origin.” Journal on Migration and Human Security, December 22, 2022.

Warren, Robert. “After a Decade of Decline, the U.S. Undocumented Population Increased by 650,000 in 2022.” Center for Migration Studies of New York, January 28, 2024.

Warren, Robert. “The Undocumented Population in the United States Increased to 12.2 Million in 2023.” Journal on Migration and Human Security 13(4): 497–504, 2025.

Center for Migration Studies of New York. “State and National Data Tool: Estimates of Undocumented and Eligible-to-Naturalize Populations by State.” 2026.

Migration Policy Institute

Passel, Jeffrey S. “New Estimates of the Undocumented Population in the United States.” Migration Policy Institute, May 22, 2002.

Van Hook, Jennifer, and Jeffrey S. Passel. “Unauthorized Migrants Living in the United States: A Mid-Decade Portrait.” Migration Policy Institute, September 1, 2005.

Van Hook, Jennifer, Julia Gelatt, and Ariel G. Ruiz Soto. “A Turning Point for the Unauthorized Immigrant Population in the United States.” Migration Policy Institute, September 2023.

Van Hook, Jennifer, Ariel G. Ruiz Soto, and Julia Gelatt. “The Unauthorized Immigrant Population Expands amid Record U.S.-Mexico Border Arrivals.” Migration Policy Institute, February 2025.

Ruiz Soto, Ariel G., Julia Gelatt, and Jennifer Van Hook. “Following Years of High Border Arrivals, the U.S. Unauthorized Immigrant Population Hits New Peak.” Migration Policy Institute, July 29, 2026.

Migration Policy Institute. “The U.S. Unauthorized Immigrant Population Reaches New Levels and Diversifies, MPI Estimates Show.” July 29, 2026.

Pew Research Center

Passel, Jeffrey S., and Jens Manuel Krogstad. “U.S. Unauthorized Immigrant Population Reached a Record 14 Million in 2023.” Pew Research Center, August 21, 2025.

U.S. Department of Homeland Security

Baker, Bryan. “Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2015–January 2018.” Office of Immigration Statistics, U.S. Department of Homeland Security, January 2021.

Baker, Bryan and Warren, Robert. “Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2018–January 2022.” Office of Homeland Security Statistics, U.S. Department of Homeland Security, April 2024.

Elizabeth M. Grieco, Ph.D.
Independent Researcher
August 24, 2026

Website: elizabethgrieco.com