Immigration by the numbers: DHS has no idea how many people are entering illegally
Illegal immigration, by the numbers: Visa violators and border crossers
No one knows exactly how many undocumented aliens are in the United States, or from where they come. Most estimates range wildly, from 10 million to 22 million.
What we do know, from various studies and estimates, is that Central Americans illegally crossing the U.S.-Mexico border are not the only source of our problem.
Undocumented aliens come here from all over the world - and visa overstays are as great a problem as those illegal border crossings shown nightly on TV and debated endlessly in Congress.
The inherent difficulty in calculating the numbers is that undocumented aliens usually avoid drawing attention to their status, to avoid being deported.
In February 2018, the Center for Migration Studies estimated 10.8 million undocumented aliens living here in 2016. Last December, the Department of Homeland Security (DHS) estimated 12 million undocumented aliens as of January 2015. On June 3, Pew Research Center put the number 10.7 million in 2016.
None of these estimates seems reliable. They are based on Census Bureau data: The number of legal immigrants in the country was subtracted from the number of census participants who acknowledged they were not born in the U.S.
Yet, Census information is self-reported by survey participants with no independent verification. There's no way of knowing if a significant percentage of the undocumented alien population participated. And it is utterly unrealistic to expect undocumented aliens to admit their status in surveys conducted by the federal government.
Professors from MIT and Yale, using more sophisticated methodology, estimated in September 2018 that 22.1 million undocumented aliens are in the U.S. Their estimate is based on operational data such as border apprehensions, deportations, visa overstays and demographic figures, as well as mortality and emigration rates. They evaluated the data with a mathematical model that estimates and tracks population inflows and outflows.
Yet, some of these factors are not wholly reliable. For instance, the professors acknowledged concern about the accuracy of apprehension data: "We don't know the number of people who cross the border successfully - we only know when people get caught trying."
The visa overstay numbers they used may not be accurate, either.
An "overstay" is a non-immigrant visitor who was admitted for a specified time but remained longer without permission. Most overstay data pertains to non-immigrant visitors who came here through the Visa Waiver Program, which allows eligible aliens from 38 countries to enter the United States as non-immigrant visitors without going through the visa process.
Although the Visa Waiver Program was established in 1986 and entries began in 1988, overstay records were not available until 2016. Moreover, entry and exit data is only collected at air- and seaports; it is not collected at land ports.
The DHS "Fiscal Year 2018 Entry/Exit Overstay Report" indicates 666,582 suspected overstay "events" in fiscal 2018. That includes 68,593 students or exchange visitors and other categories of non-immigrants who entered with visas.
The term "event" refers to the number of "expected departures," not to the number of actual aliens who were expected to depart - and the Center for Immigration Studies claims this makes the overstay rates deceptively low.
To explain, using DHS methodology: If 10 non-immigrant visitors enter the U.S. three times each in a year, that would result in a total of 30 "expected departures." If they all leave as required, but an additional visitor makes only one visit and overstays, the overstay rate would be 1 in 31 entries, or about 3 percent. Yet, if the overstay rate were calculated by counting people, the rate would be 1 in 11, or about 9 percent.
According to the Center for Migration Studies, the number of known overstays significantly exceeded illegal border crossings from 2010 to 2017.
Where are they from?
The following table from the DHS "2017 Yearbook of Immigration Statistics" provides data on the regions apprehended aliens come from. It includes Border Patrol apprehensions and Immigration and Customs Enforcement (ICE) administrative arrests.
A breakdown of which countries they are from can be found on page 92 of the Yearbook.
While migrants apprehended at the Southwest border once predominantly came from Mexico, most now come from the "Northern Triangle" - El Salvador, Guatemala and Honduras.
CBP statistics indicate illegal border crossing apprehensions have risen dramatically along the Southwest border - from 51,008 in October 2018, to 132,887 in May 2019.
Reducing the numbers
Deporting those who have just made an illegal entry does not reduce the population of undocumented aliens. It just prevents it from getting larger.
To reduce that population, illegal residents would have to be removed from the interior of the country - and the immigration court backlog crisis severely limits such removals. So, too, does the difficulty of identifying and finding illegal residents, the limited numbers of ICE officers who could be assigned to that task, and the notoriously limited cooperation provided by some state and local governments, among many factors.
The "Fiscal Year 2018 ICE Enforcement and Removal Operations Report" shows how many aliens were removed from the interior of the country between fiscal 2016 and fiscal 2018. It reports that the number rose steadily - from 65,332 in 2016, to 81,603 in 2017 and 95,360 in 2018.
Still, each of those figures is but a fraction of the millions estimated to be living here illegally - and they only serve to underscore the magnitude of the immigration crisis we face.
Nolan Rappaport was detailed to the House Judiciary Committee as an executive branch immigration law expert for three years. He subsequently served as an immigration counsel for the Subcommittee on Immigration, Border Security and Claims for four years. Prior to working on the Judiciary Committee, he wrote decisions for the Board of Immigration Appeals for 20 years. Follow him on Twitter @NolanR1