This paper combines data from two reports by the Center for Migration Studies (CMS) with Department of Homeland Security (DHS) statistics on apprehensions, adjustment of status, and removals, to illustrate major trends in undocumented immigration to the United States since 1990. It shows that the undocumented population and undocumented migration to the United States — which includes both entries without inspection (EWIs) and overstays of temporary visas — have fallen dramatically. In particular, the undocumented population has declined by one million since 2010; illegal entries have plummeted to historic lows; and, in recent years only one third of newly undocumented residents entered this population by crossing the southern border.
The paper includes four graphs that illustrate major demographic trends in the undocumented population since 2000 and a table that provides detailed information about the size and components of undocumented population change annually since 1990.
- Undocumented population growth peaked in 2000, then dropped rapidly from 2000 to 2010; the total population has declined by one million since 2010 (Figure 1).
- The drop in DHS apprehensions at the border mirrored the decline in undocumented population growth, falling from 1.6 million in 2000 to about 300,000 in 2017 (Figure 2).
- Undocumented population growth stopped because undocumented arrivals fell from 1.4 million in 2000 to about 550,000 in 2007 and continued at about that level; the number leaving the population increased steadily, from 370,000 in 2000 to 770,000 in 2016 (Figure 3 and Table 1).
- From 2010 to 2016, about two thirds of undocumented arrivals overstayed temporary visas; only one third entered across the southern border. Overstays exceeded EWIs after 2008 because EWIs continued to decline while overstays remained stable (Figure 4).
The trends illustrated below demonstrate the substantial progress that has been made since 2000 in reducing undocumented migration and reversing undocumented population growth. The most likely reasons for these sharp declines are increases in enforcement at the southern border during the Bush and Obama administrations and improved economic and demographic conditions in Mexico. Overall, despite the rise in applications for asylum at the southern border, undocumented migration to the United States today is lower than it has been in the past 25 years (Table 1). Applicants for asylum should not be included in statistics on undocumented immigration. However, because of limitations in the data, many of them are erroneously included as undocumented residents. This erroneous classification of asylum seekers — who are exercising a right recognized under international and domestic law — accounts for some of the increase in arrivals after 2012 shown in Table 1, column 3.
Figure 1 shows the steep drop in undocumented population growth, from about one million in 2000 to near or below zero growth after 2008. All the estimates shown in this paper are subject to sampling and non-sampling errors; nevertheless, such errors would likely be spread over the entire period, and thus would not be likely to affect the trends shown here.
Figure 2 shows DHS data for apprehensions of undocumented residents at the southern border from 2000 to 2017. The remarkable 81 percent decline in apprehensions, from 1.6 million in 2000 to about 300,000, occurred even though the size of the Border Patrol more than doubled, from 9,200 in 2000 to 19,400 in 2017 (CBP 2017b). These statistics strongly support the estimates of declining population growth shown in Figure 1 and the sharp drop in arrivals of undocumented residents from 2000 to 2010 shown in Figure 3. That is, if arrivals across the border had not been falling rapidly, the number of apprehensions would have increased as the size of the Border Patrol increased.
Figure 3 shows why population growth fell so rapidly after 2000 — arrivals dropped from 1.4 million in 2000 to fewer than 400,000 in 2009, a decline of more than 70 percent (Table 1). Meanwhile, the number of departures from the population steadily increased, from 370,000 in 2000 to about 770,000 in 2016. Annual statistics on departures from the undocumented population, including through emigration (voluntary departures), adjustment of status, removal by DHS, and death, are shown in Table 1.
Figure 4 shows estimates of undocumented arrivals from 2000 to 2016 separately for entries across the border and for overstays. Overstays exceeded EWIs beginning in about 2008 and overstays accounted for two thirds of total entries after 2010. As Figure 4 shows, arrivals of EWIs dropped from 945,000 in 2000 to 210,000 in 2016. Overstays were at about the same level in 2000 (445,000) as they were in 2016 (410,000).
The increase in overstays after 2010 in Figure 4 is primarily the result of increases in the undocumented population from India and Venezuela. The population from India increased from 336,000 in 2010 to 629,000 in 2017; the population from Venezuela increased from 65,000 in 2010 to 146,000 in 2017, with most of the increase occurring in 2015 and 2016.
Certainly, there is a strong need to address the conditions driving the high numbers of asylum seekers, particularly from the Northern Triangle States of Central America, to the United States; to better secure and to expand the infrastructure at US ports of entry; and to adjust US border enforcement strategies in response to evolving challenges. However, the multiyear trends described in this paper suggest significant progress at the US-Mexico border, not a national emergency (White House 2019).
 Warren and Warren (2013) and Warren (2019).
 Note, however, that two countries had fast-growing populations from 2010 to 2017: India, which grew by 265,000, and Venezuela, which grew by 80,000. Nearly all of the undocumented arrivals from these countries are overstays.
 For each year of arrival, the total of overstays and EWIs shown in Figure 4 agrees with total additions to the population shown in Figure 3.
 Annual estimates of overstays and EWIs are based on 2017 CMS estimates of arrivals from each country, distributed to overstays and EWIs using the percentages shown in Warren and Kerwin (2017, Table A-2).
CBP (US Customs and Border Protection). 2017a. “Southwest Border Sectors: Total Illegal Alien Apprehensions by Fiscal Year (Oct. 1st through Sept. 30th).” Washington, DC: CBP. https://www.cbp.gov/sites/default/files/assets/documents/2017-Dec/BP%20Southwest%20Border%20Sector%20Apps%20FY1960%20-%20FY2017.pdf.
———. 2017b. U.S. Border Patrol Fiscal Year Staffing Statistics (FY 1992 – FY 2017). Washington, DC: CBP. https://www.cbp.gov/document/stats/us-border-patrol-fiscal-year-staffing-statistics-fy-1992-fy-2017.
Warren, Robert, and Donald Kerwin. 2017. “The 2,000 Mile Wall in Search of a Purpose: Since 2007 Visa Overstays have Outnumbered Undocumented Border Crossers by a Half Million.” Journal on Migration and Human Security 5(1): 124-36. https://doi.org/10.1177/233150241700500107.
Warren, Robert, and John Robert Warren. 2013. “Unauthorized Immigration to the United States: Annual Estimates and Components of Change, by State, 1990 to 2010.” International Migration Review 47(2): 296-329. https://doi.org/10.1111/imre.12022.
Warren, Robert. 2019. “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 7(1): 19-22. https://doi.org/10.1177/2331502419830339.
White House. 2019. “Remarks by President Trump on the National Security and Humanitarian Crisis on our Southern Border.” Speech, Washington, DC, February 15. https://www.whitehouse.gov/briefings-statements/remarks-president-trump-national-security-humanitarian-crisis-southern-border/.