Illegal Immigration, Population Estimates in the United States, 1969-2016
See below for research on population estimates of undocumented immigrants (graph), their relative percentage of the overall US population (graph and chart), and the sources of that information.
I. Graph of Population Estimates of Immigrants in the Country Illegally in Millions
II. Graph of Total US Population Compared to Population of Immigrants in the Country Ilegally
Sources by year below. Official US government sources used when available. The source for 2008, 2003, and 2002 is Jeffrey Passel and D'Vera Cohn, "Unauthorized Immigrants: 11.1 Million in 2011," pewhispanic.org, Dec. 6, 2012.
III. Chart of Population of Immigrants in the Country Illegally Compared to the Total US Population
Population of Immigrants in the Country Illegally (with link to source)
Total US Population (according to US Census data)
% of US Population that Is Immigrants in the Country Illegally
Sources by year below. Official US government sources used when available. The source for 2008, 2003, and 2002 is Jeffrey Passel and D'Vera Cohn, "Unauthorized Immigrants: 11.1 Million in 2011," pewhispanic.org, Dec. 6, 2012
IV. Chart of Population Estimates of Immigrants in the Country Illegally
Estimated Number of Immigrants in the Country Illegally
Quote, Date, and Source
(with links to source biography and full text of report if available)
"There were 11 million unauthorized immigrants in the U.S. in 2015, a small but statistically significant decline from the Center’s estimate of 11.3 million for 2009. The Center’s preliminary estimate of the unauthorized immigrant population in 2016 is 11.3 million, which is statistically no different from the 2009 or 2015 estimates because it is based on a data source with a smaller sample size and larger margin of error. Unauthorized immigrants represented 3.4% of the total U.S. population in 2015. The number of unauthorized immigrants peaked in 2007 at 12.2 million, when this group was 4% of the U.S. population."
Pew Research Center, "Unauthorized Immigrant Population Stable for Half a Decade," pewresearch.org, Apr. 27, 2017
"An estimated 11.3 million unauthorized immigrants lived in the U.S. in 2014, according to a new preliminary Pew Research Center estimate based on government data. This population has remained essentially stable for five years after nearly two decades of changes.
The recent overall stability contrasts with past trends. The unauthorized immigrant population had risen rapidly during the 1990s and early 2000s, from an estimated 3.5 million in 1990 to a peak of 12.2 million in 2007. It then dropped sharply during the Great Recession of 2007-09, mainly because of a decrease in immigration from Mexico."
Pew Research Center, "Unauthorized Immigrant Population Stable for Half a Decade," pewresearch.org, July 22, 2015
"There were 11.3 million unauthorized immigrants living in the U.S. in March 2013, according to preliminary Pew Research Center estimate, about the same as the 11.2 million in 2012 and unchanged since 2009. The population had risen briskly for decades before plunging during the Great Recession of 2007 to 2009."
Pew Research Center, "As Growth Stalls, Unauthorized Population Becomes More Settled," pewresearch.org, Sep. 3, 2014
"[A]n estimated 11.4 million unauthorized immigrants were living in the United States in January 2012 compared to 11.5 million in January 2011. These results suggest little to no change in the unauthorized immigrant population from 2011 to 2012."
"[A]n estimated 11.5 million unauthorized immigrants were living in the United States in January 2011 compared to a revised 2010 estimate of 11.6 million. These results suggest little to no change in the unauthorized immigrant population from 2010 to 2011. It is unlikely that the unauthorized immigrant population increased after 2007 given relatively high U.S. unemployment, improved economic conditions in Mexico, record low numbers of apprehensions of unauthorized immigrants at U.S. borders, and greater levels of border enforcement. Of all unauthorized immigrants living in the United States in 2011, 55 percent entered between 1995 and 2004. Entrants since 2005 accounted for only 14 percent of the total. Fifty-nine percent of unauthorized immigrants in 2011 were from Mexico."
"In summary, DHS estimates that the unauthorized immigrant population living in the United States decreased to 10.8 million in January 2009 from 11.6 million in January 2008. Between 2000 and 2009, the unauthorized population grew by 27 percent. Of all unauthorized immigrants living in the United States in 2009, 63 percent entered before 2000, and 62 percent were from Mexico."
"In summary, an estimated 11.8 million unauthorized immigrants were living in the United States in January 2007 compared to 8.5 million in 2000 (Hoefer, Rytina, and Campbell, 2006). Between 2000 and 2007, the unauthorized population increased 3.3 million; the annual average increase during this period was 470,000. Nearly 4.2 million (35 percent) of the total 11.8 million unauthorized residents in 2007 had entered in 2000 or later. An estimated 7.0 million (59 percent) were from Mexico."
"Our best estimate, based on the March 2002 Current Population Survey and other data sources, is that there are 9.3 million undocumented immigrants in the country. They represent 26 percent of the total foreign-born population."
Urban Institute, "Undocumented Immigrants: Facts and Figures," urban.org, Jan. 12, 2004
"In the case of the total unauthorized population, we estimate that the size of this group in mid-2001 varies from a low of about 5.9 million to a high of about 9.9 million, with a mid-range estimate of about 7.8 million. In the case of the Mexican unauthorized population, we estimate that the size of this group varies from a low of about 3.4 million to a high of about 5.8 million, with a mid-range estimate of about 4.5 million. In the case of the non-Mexican Central American unauthorized population, we estimate that the size of this group varies from a low of about 1.2 million to a high of about 1.9 million, with a mid-range estimate of about 1.5 million."
Pew Research Center, "Estimates of Numbers of Unauthorized Migrants Residing In the United States," pewresearch.org, Jan. 24, 2002
"DHS [Department of Homeland Security] estimates that the unauthorized immigrant population in the United States increased 24 percent from 8.5 million on January 1, 2000 to 10.5 million on January 1, 2005."
"In its last set of estimates, INS [Immigration and Naturalization Service] estimated that the population was 5.0 million in October 1996... In 1994, the INS developed the first detailed national estimates of the unauthorized immigrant population residing in the United States. Those estimates indicated that the unauthorized resident population was 3.4 million as of October 1992."
"[T]he 'April 1983 [U.S. Census Bureau] Current Population Survey' included over two million (2,093,000) undocumented aliens aged fourteen years and over... Just over 30 percent of the two million entered the United States during 1980-1983 and nearly one-half came to the country during the 1970s."
US Census Bureau, "Change in the Undocumented Alien Population in the United States, 1979-1983," census.gov, Winter 1987
"[E]stimates of the number counted in the census  provide a firm empirical basis for setting a lower bound on the total in the country as of 1980. The estimates presented in this paper, along with the results of other studies (Panel on Immigration Statistics, 1985), suggest that the undocumented Mexican population in 1980 was in the 1-2 million range, with the total number from all countries falling in the range of 2-4 million. [...] Of the undocumented present and counted in 1980, 941,000 entered during 1975-1980; 576,000 entered during 1970-1974; and 540,000 entered before 1970 [and after passage of the Immigration Act of 1965]. [...] Finally, the estimates for 1980 show a high proportion of recent arrivals, and very few who entered the United States prior to 1960."
Robert Warren and Jeffrey S. Passel, "A Count of the Uncountable: Estimates of Undocumented Aliens Counted in the 1980 United States Census," Demography, Aug. 1987
** Average between 2 and 4 million
*** Sum of 540,000 (1969) and 576,000 (1970 - 1974)
**** "before 1970" and after 1965 was interpreted by ProCon.org to mean as of 1969
[Editor's Note: On March 27, 2007, we called the US Census Bureau to get pre-1970 statistics, and were told that the "Census survey does not ask for legal status information," and that the existing estimates are based on "residual studies" which were not available until the 1970s. We also called the Department of Homeland Security Office of Immigration Statistics and were told that "data prior to 1970 are scarce," and "early estimates are not reliable." We did find a statement from the US General Accounting Office explaining why pre-1970 information is so hard to find:
"The illegal alien population is constantly in flux. Individuals enter and exit this population daily by making covert border crossings, by taking unauthorized employment, by failing to leave when their visas expire, by dying, and as a result of INS [Immigration and Naturalizations Service] decisions. Policymakers need to know the size of the population at particular moments and the volume of immigration over periods of time. Although illegal immigration has been a concern since the introduction of immigration curbs in 1875, deliberate attempts to estimate the population size reliably were not made until the 1970's."