How many illegal immigrants are there in the United States?
Short Answer
Because unauthorized migrants are not directly counted, researchers must estimate their number by combining multiple data sets and assumptions.
- The most widely-cited demographic studies from Pew Research Center and the U.S. Department of Homeland Security put the total near 10 – 11 million people in recent years, down slightly from a peak in 2007.[2][3]
- A 2018 study by scholars at Yale, MIT, and other institutions argued that the real figure could be roughly double that—about 16.7 – 22.1 million, with a mid-point of 19.6 million in 2016.[1]
In short, credible academic and government estimates today range from about 10 million to a little over 20 million unauthorized immigrants living in the United States.
Current Estimates
- Pew Research Center (most recently using 2021 data) estimates 10.5 million unauthorized immigrants, representing roughly 3.0 % of the total U.S. population.[2]
- The U.S. Department of Homeland Security’s Office of Immigration Statistics (OIS) estimates 11.4 million for 2018, with only modest year-to-year changes since 2015.[3]
- Yale-MIT study (Fazel-Zarandi, Feinstein, Kaplan, et al.) recalculated the same period and arrived at a much higher range—16.7 – 22.1 million for 2016, contending that traditional “residual” methods undercount overstays and census-missed residents.[1]
Why Estimates Differ
- Data sources. Government figures start with Census Bureau surveys (ACS, CPS) and deduct lawful immigrants and temporary visa holders. Critics say these surveys miss hard-to-reach households.[1]
- Undercount assumptions. Pew and DHS assume a census undercount of roughly 15 % for unauthorized immigrants; the Yale-MIT team models a wider possible undercount, leading to a larger final number.[1][2]
- Treatment of visa overstays. Pew and DHS treat administrative records of temporary visas as largely complete, whereas the Yale-MIT study models additional long-term overstays they believe are not fully captured.[1]
- Time frame. Most estimates refer to a single year and are updated periodically; differences in reference year can add confusion in public discussion.[2][3]
Public Discourse
The gap between the “10 million” and “20 million” camps has become a talking point in policy and media debates. Supporters of the larger estimate argue that more accurate numbers are vital for funding, enforcement planning, and economic analysis. Critics respond that the Yale-MIT model relies on assumptions that may overstate long-term overstays and double-count certain populations.
Both sides generally agree that:
- The unauthorized population has plateaued or declined modestly since the Great Recession.
- Better data—particularly on visa overstays and census undercounts—would narrow the range of plausible estimates.
Until such data become available, the academic literature will likely continue to present a band of possible totals rather than a single uncontested figure.
Sources
- MIT Sloan School of Management. “Study: undocumented immigrant population roughly double current estimate.” (2018) https://mitsloan.mit.edu/ideas-made-to-matter/study-undocumented-immigrant-population-roughly-double-current-estimate
- Pew Research Center. “Facts on U.S. unauthorized immigrants.” (2022 update using 2021 ACS) https://www.pewresearch.org/short-reads/2022/11/29/facts-on-u-s-unauthorized-immigrants/
- U.S. Department of Homeland Security, Office of Immigration Statistics. Baker, B. “Estimates of the unauthorized immigrant population residing in the United States: January 2015–January 2018.” (2021) https://www.dhs.gov/sites/default/files/2021-02/immigration-statistics/PopEstimate/UnauthImmigrant/unauthorizedimmigrantpopulationestimates2015-_2018.pdf