The unauthorized immigrant population in the United States reached 10.5 million in 2021, according to new Pew Research Center estimates. That was a modest increase over 2019 but nearly identical to 2017.
The number of unauthorized immigrants living in the U.S. in 2021 remained below its peak of 12.2 million in 2007. It was about the same size as in 2004 and lower than every year from 2005 to 2015.
The new estimates do not reflect changes that have occurred since apprehensions and expulsions of migrants along the U.S.-Mexico border started increasing in March 2021. Migrant encounters at the border have since reached historic highs.
Pew Research Center undertook this research to understand ongoing changes in the size and characteristics of the unauthorized immigrant population in the United States. The Center has published estimates of the U.S. unauthorized immigrant population for more than two decades. The estimates presented in this research are the Center’s latest, adding new and updated annual estimates for 2017 through 2021.
Center estimates of the unauthorized immigrant population use a “residual method.” It is similar to methods used by the U.S. Department of Homeland Security’s Office of Immigration Statistics and nongovernmental organizations, including the Center for Migration Studies and the Migration Policy Institute. Those organizations’ estimates are generally consistent with ours. Our estimates also align with official U.S. data sources, including birth records, school enrollment figures and tax data, as well as Mexican censuses and surveys.
Our “residual” method for estimating the nation’s unauthorized immigrant population includes these steps:
- Estimate the total number of immigrants living in the country in a particular year using data from U.S. censuses and government surveys such as the American Community Survey and the Current Population Survey.
- Estimate the number of immigrants living in the U.S. legally using official counts of immigrant and refugee admissions together with other demographic data (for example, death and out-migration rates).
- Subtract our estimate of lawful immigrants from our estimate of the total immigrant population. This provides an initial estimate of the unauthorized immigrant population.
Our final estimate of the U.S. unauthorized immigrant population, as well as estimates for lawful immigrants, includes an upward adjustment. We do this because censuses and surveys tend to miss some people. Undercounts for immigrants, especially unauthorized immigrants, tend to be higher than for other groups. (Our 1990 estimate comes from work by Robert Warren and John Robert Warren; details can be found here.)
The term “unauthorized immigrant” reflects standard and customary usage by many academic researchers and policy analysts. The U.S. Department of Homeland Security’s Office of Immigration Statistics also generally uses it. The term means the same thing as undocumented immigrants, illegal immigrants and illegal aliens.
For more details on how we produced our estimates, read the Methodology section of our November 2018 report on unauthorized immigrants.
Here are key findings about how the U.S. unauthorized immigrant population changed from 2017 to 2021:
- The most common country of birth for unauthorized immigrants is Mexico. However, the population of unauthorized immigrants from Mexico dropped by 900,000 from 2017 to 2021, to 4.1 million.
- There were increases in unauthorized immigrants from nearly every other region of the world – Central America, the Caribbean, South America, Asia, Europe and sub-Saharan Africa.
- Among U.S. states, only Florida and Washington saw increases to their unauthorized immigrant populations, while California and Nevada saw decreases. In all other states, unauthorized immigrant populations were unchanged.
- 4.6% of U.S. workers in 2021 were unauthorized immigrants, virtually identical to the share in 2017.
Trends in the U.S. immigrant population
The U.S. foreign-born population was 14.1% of the nation’s population in 2021. That was very slightly higher than in the last five years but below the record high of 14.8% in 1890.
As of 2021, the nation’s 10.5 million unauthorized immigrants represented about 3% of the total U.S. population and 22% of the foreign-born population. These shares were among the lowest since the 1990s.
Between 2007 and 2021, the unauthorized immigrant population decreased by 1.75 million, or 14%.
Meanwhile, the lawful immigrant population grew by more than 8 million, a 29% increase, and the number of naturalized U.S. citizens grew by 49%. In 2021, naturalized citizens accounted for about half (49%) of all immigrants in the country.
Where unauthorized immigrants come from
Unauthorized immigrants living in the U.S. come from many parts of the world, with Mexico being the most common origin country.
The origin countries for unauthorized immigrants have changed since the population peaked in 2007, before the Great Recession slowed immigration. Here are some highlights of those changes:
The number of unauthorized immigrants from Mexico living in the U.S. (4.1 million in 2021) was the lowest since the 1990s. Mexico accounted for 39% of the nation’s unauthorized immigrants in 2021, by far the smallest share on record.
The decrease in unauthorized immigrants from Mexico reflects several factors:
- A broader decline in migration from Mexico to the U.S.
- Mexican immigrants to the U.S. continuing to return to Mexico
- Expanded opportunities for lawful immigration from Mexico and other countries, especially for temporary agricultural workers.
The rest of the world
The total number of unauthorized immigrants in the U.S. from countries other than Mexico has grown rapidly. In 2021, this population was 6.4 million, up by 900,000 from 2017.
Almost every region in the world had a notable increase in the number of unauthorized immigrants in the U.S. from 2007 to 2021. The largest increases were from Central America (240,000) and South and East Asia (180,000).
After Mexico, the countries of origin with the largest unauthorized immigrant populations in the U.S. in 2021 were:
- El Salvador (800,000)
- India (725,000)
- Guatemala (700,000)
- Honduras (525,000)
India, Guatemala and Honduras all saw increases from 2017.
The Northern Triangle
Three Central American countries – El Salvador, Honduras and Guatemala – together represented 2.0 million unauthorized immigrants in the U.S. in 2021, or almost 20% of the total. The unauthorized immigrant population from the Northern Triangle grew by about 250,000 from 2017 and about 700,000 from 2007.
Other origin countries
Venezuela was the country of birth for 190,000 U.S. unauthorized immigrants in 2021. This population saw particularly fast growth, from 130,000 in 2017 and 55,000 in 2007.
Among countries with the largest numbers of U.S. unauthorized immigrants, India, Brazil, Canada and former Soviet Union countries all experienced growth from 2017 to 2021.
Some origin countries with significant unauthorized immigrant populations showed no change, notably China (375,000) and the Dominican Republic (230,000).
U.S. states of residence of unauthorized immigrants
The unauthorized immigrant population in most U.S. states stayed steady from 2017 to 2021. However, four states saw significant changes:
- Florida (+80,000)
- Washington (+60,000)
- California (-150,000)
- Nevada (-25,000)
States with the most unauthorized immigrants
The six states with the largest unauthorized immigrant populations in 2021 were:
- California (1.9 million)
- Texas (1.6 million)
- Florida (900,000)
- New York (600,000)
- New Jersey (450,000)
- Illinois (400,000)
These states have consistently had the most unauthorized immigrants since 1990 and earlier.
At the same time, the unauthorized immigrant population has become less geographically concentrated. In 2021, these six states were home to 56% of the nation’s unauthorized immigrants, down from 80% in 1990.
Detailed table: Unauthorized immigrant population for states (and margins of error), 1990-2021 (Excel)
Detailed table: Unauthorized immigrants and characteristics for states, 2021 (Excel)
Unauthorized immigrants in the labor force
The share of unauthorized immigrants in the U.S. workforce was slightly less than 5% in 2021, compared with 3% of the total U.S. population.
Demographics help explain the difference: The unauthorized immigrant population includes relatively few children or elderly adults, groups that tend not to be in the labor force.
Overall, about 7.8 million unauthorized immigrants were in the U.S. labor force in 2021. That was up slightly from 2019 but smaller than every year from 2007 through 2015.
Detailed table: Unauthorized immigrants in the labor force for states, 2021 (Excel)
Here are some additional findings about unauthorized immigrants as a share of the workforce nationwide and in certain states:
- Since 2003, unauthorized immigrants have made up 4.4% to 5.4% of all U.S. workers, a relatively narrow range.
- Fewer than 1% of workers in Maine, Montana, Vermont and West Virginia in 2021 were unauthorized immigrants.
- Nevada (9%) and Texas (8%) had the highest shares of unauthorized immigrants in the workforce.