How Many Illegals Live in the U.S.? - What Everyone ‘Knows’ Is Not True

By Edwin S. Rubenstein
Volume 27, Number 2 (Winter 2017)
Issue theme: "Importing diseases"

The Winter 2017 Social Contract (hard copy) contains an article under my byline titled, "How Many Illegals Live in the U.S.? What Everyone 'Knows" Is Not True." Much of the material in the first part of this piece is taken from William Campenni's article, "You Only Think You Know How Many Illegal Immigrants Live in the U.S.," which appeared in The Daily Signal, December 27, 2015. Although I cite Mr. Campenni once, there are paragraphs of his that lack attribution — an oversight corrected in this digital version. I regret the oversight, and commend him for writing a great article on this important topic. — E.R.

Call any journalist, pundit, anchor, strategist or lobbyist and ask” 1. How many illegal immigrants are in the United States, and 2. What is the source for that number? Almost without exception you will receive the following answers: 1. 11 million. 2. The Pew Research Center.”—William Campenni, The Daily Signal, December 27, 2015.

“For a decade now,” Compenni notes, “no number has been accorded greater certitude and less close examination than that [11 million figure].” Sure, the number of illegal aliens is universally thought to have declined during the Great Recession as jobs disappeared, and risen somewhat during the long, slow “recovery.” But neither the peak nor the low point over that period deviates more than 1 or 2 million from the consensus 11 million figure.

DHS’s latest estimate of the size of the undocumented immigrant population — 11.4 million in January 2012 — is down from a peak of 11.8million in 2007.1 This count includes people who entered the United States illegally and people who overstayed their visas. The Pew Research Center estimate for 2012 was 11.2 million, while CIS estimates the illegal alien population that year to be in the range of 11 to 12 million.2

Such unanimity may seem surprising given the different political orientations of these research organizations. Homeland Security is a bureaucracy with a presidentially appointed secretary who carries out administration policies. Pew claims impartiality, but the same organization is home to the Pew Hispanic Center, a decidedly pro-immigration group with close links to the liberal Brookings Institution and the Urban Institute. The Center for Immigration Studies favors controlling and limiting immigration flows to the U.S.

On the other hand, unanimity is exactly what you would expect given that each group starts with Census Bureau data — from either the Current Population Survey or the American Community Survey — in estimating the illegal alien population. The surveys are conducted both by mail and in-person visits to selected homes. Neither asks directly, “Are you in the United States illegally?”

In fact, the instruction manual for the Current Population Survey canvassers states explicitly: “We do not ask for nativity data to identify illegal immigrants. Note that we ask whether a person is a citizen, and that we do not ask whether he/she is legal or not (that is, has a green card or some other legal residence status).”3

Each estimate relies on what is called the residual method of estimation, which starts with A (total foreign born), subtracts B (legal immigrants), to arrive at C (estimated number of illegal immigrants.)

The first data point — A, the total foreign-born population — is rarely scrutinized because it is so readily available. Every Census survey asks respondents where they were born. The problem is that each relies on the candor of those who are surveyed. Households containing members who are illegal aliens are less likely to return survey mailings, and when followed up with personal interviews, are less likely to identify those individuals.4

Undercounts are the inevitable result. In estimating the foreign-born population in 2012, DHS added 2.326 million to the figure reported by the American Community Survey (ACS).5 The adjustment includes 1.140 million for the undercount of illegals in ACS, 520,000 for the undercount of legal immigrants in ACS, and 190,000 for the undercount of nonimmigrants. The actual undercount, of course, could be far larger.

Estimating the number of legal immigrants — B — is equally tricky. While Homeland Security knows exactly how many individuals are awarded Legal Permanent Resident (LPR), refugee, and asylee status each year, only the Census knows — or should know — how many of these folks actually arrive in the U.S. each year. International migration records both into and out of the country are problematic. Homeland Security estimates that 4.01 million of the 26.64 million legal immigrants admitted to the U.S. between 1980 and 2011 went back (emigrated) during that time, and 1.84 million died in this country.

The components of Homeland Security’s illegal alien calculation for 2012 are as follows:

Total foreign-born population (A): 34,090,000

Legal immigrants (B): 22,660,000

Illegal immigrants (C = A – B): 11,430,000

Note that A, the foreign-born population figure, is considerably below the 40 million-plus number we are familiar with. Homeland Security’s figure reflects only those immigrants who arrived since 1980. DHS explains: “Foreign-born residents who entered the United States prior to 1980 were assumed to be legally resident since most were eligible for LPR status.”6


In effect, DHS declares all of the roughly 10 million illegals who arrived prior to 1980 to be legal no matter how they arrived here. That is a red flag: no illegal entrant, no matter how long in this country, should be given a lifetime pass. But there are other, more important questions regarding the integrity of Homeland Security’s estimates of the illegal immigrant population. Just look at the trend — or lack of same.

To keep that 11 million a near constant you would have to assume the influx of illegals is offset by those leaving voluntarily or dying in similar numbers. But we haven’t seen reports of a massive southbound crush across the Rio Grande or a deadly epidemic attacking undocumented aliens. A stagnant illegal alien population simply does not make sense in light of the agency’s own data on Border Patrol apprehensions along the southwestern border: Over the 2006 to 2012 period, 4.3 million border crossers were apprehended.7

Border Patrol apprehensions along the Southwestern Border peaked at about 1.64 million in 2000. Since that year they have declined precipitously. In fiscal year (FY) 2015 331,335 border crossers were apprehended, a 31 percent drop from FY2014, and a whopping 80 percent decline from FY2000:


While the trend is down, annual apprehensions are still high — in the 300,000 to 500,000 range. More importantly, over the 2000 to 2015 period a total of 12.6 million illegals were apprehended along the Southwestern border. Despite the massive influx, Homeland Security estimates that the illegal alien population rose by just 2.9 million — from 8.5 million in 2000 to 11.4 million in 2012. This implies that about 81 percent all border crossers are apprehended, and only 19 percent succeed in getting in.

At least one Border Patrol agent has blown the whistle on this claim.

Reality check

One of the Department of Homeland Security’s fiscal 2016 goals is for the Border Patrol to interdict 81 percent of the persons it detects illegally entering the U.S. between ports of entry on the U.S.-Mexico border. To measure this goal and determine the Border Patrol’s effectiveness in meeting it, Homeland Security calculates the “Interdiction Effectiveness Rate” (IER), describing it in an appendix to its latest performance report:8

This measure reports the percent of detected illegal entrants who were apprehended or turned back after illegally entering the United States between the ports of entry on the Southwest border. The Border Patrol achieves this desired strategic outcome by maximizing the apprehension of detected illegal entrants or, confirming that illegal entrants return to the country from which they entered; and by minimizing the number of persons who evade apprehension and can no longer be pursued.

Three variables — “Apprehensions,” “Turn-backs,” and “Got-aways” — are used to calculate the Interdiction Effectiveness Rate (IER). DHS defines them like this:

Apprehension: A deportable subject who, after making an illegal entry, is taken into custody and receives a consequence.

Got-away: A subject who, after making an illegal entry, is not turned back or apprehended and is no longer being actively pursued by Border Patrol agents.

Turn-back [TB]: A subject who, after making an illegal entry into the U.S., returns to the country from which he/she entered, not resulting in an apprehension or GA [Got-away].

The appendix further explains how the IER is calculated:

Calculation of the measure is done by the HQ SDI Unit [Border Patrol Headquarters Statistics and Data Integrity Unit] and is:

(Apprehensions + TB)/Total Entries. Total entries are the sum of apprehensions, TBs, and GAs.

The Interdiction Effectiveness Rate in 2015 was 81.01 percent, according to the DHS performance report. To make that calculation DHS uses three variables:

Apprehensions: 331,335
(2015 data reported by the Border Patrol)

Turn-backs: Not Available
(Data not released by the Border Patrol)

Got-aways: Not Available.
(Data not released by the Border Patrol.)

Obviously, the DHS must have estimated the number of turn-backs and got-aways in order to calculate the IER. It simply refuses to release those figures, explaining that the data are “law enforcement sensitive” and “used for intelligence and operations.”9

This is outrageous. If turn-backs are large enough, the 81 percent interdiction rate could be consistent with a million got-aways (successful border crossers). By releasing the interdiction rate without the raw numbers used to calculate it, DHS is suppressing the most crucial metric in the entire illegal immigration issue: the number of individuals it estimates are entering illegally each year.

By lumping “Turn-backs” in with “Apprehensions,” DHS is inflating the “Rate of Interdiction Effectiveness” beyond reason. Turn-backs are not “interdicted.” The vast majority will try to cross again; many of them will be future “Got-aways.”

DHS is aware of the deception. A new, as yet to be released, Homeland Security study reportedly lowers the estimated IER from 81 percent to 46 percent. The drop reflects a different, more honest, methodology. The study’s authors do not count people who turned themselves in and then immediately applied for asylum. That number was 140,000 last year, up from 20,000 a decade ago. Counting them as illegal immigration stops makes the border appear more secure than it is. In addition, the report does not include Turn-backs, people who cross over the boundary but then run back when they see Border Patrol officers.

But even the lower IER paints an overly rosy picture of border security, according to a former Border Patrol officer. Brandon Judd, president of the National Border Patrol Council, says the new report counts as successful stops thousands of people who are briefly detained but then released because of Obama administration policies.

We’ve refuted those numbers forever. Being an agent myself, I know those numbers just aren’t true … It’s just disappointing that they’ve been lying to the American people for so long.10

Judd points to a directive from the Department of Homeland Security requiring that Border Patrol officers accept the word of anyone caught near the border who says he or she has been in the United States since before January 1, 2014. Although the total number of people who fit that category is small — about 7,000 — it is growing rapidly, tripling in the first six months of the policy, according to Judd.

Much more numerous, Judd says, are illegal immigrants who are apprehended and released with notices to appear for a hearing before an immigration judge — only to disappear.

Beyond the Border Patrol

The Southwestern border, extending from the Gulf of Mexico to the Pacific Coast, is about 2,000 miles long. There are about 18,000 Border Patrol agents stationed along that border. While the manpower assigned to this sector has more than doubled since 2000, only a fraction — perhaps one in four — of illegal border crossers are apprehended by the Border Patrol. Yet this small fraction is regarded as corroborating evidence for official government estimates of the illegal alien population.

Private sector researchers, unbeholden to Census and Border Patrol figures, use data better suited to a valid estimate of this population. In 2005 a Bear Stearns study reported that “The number of illegal immigrants in the United States may be as high as 20 million people, more than double the official 9 million people estimated by the Census Bureau.”11

Bear Stearns focused on local rather than federal data: “Although the federal government has the sole authority to govern immigration flows, the responsibility for providing support to legal and illegal immigrants rests with the state and local governments…The de facto administration at the state and local level reinforces our premise that we must look at local statistics to extrapolate the most reliable headcount of immigrants.”

Looking at states where most illegal aliens live today (California, Texas, Florida, New York, Illinois, New Jersey, Arizona, Georgia, and North Carolina account for about half the undocumented population.), they found: “very dramatic increases in services required in communities that have become gateways for immigration.” These include public school enrollment, language proficiency programs, and building permits.

Bear Stearns found, these new undocumented workers were sending home significant amounts of money, suggesting that their numbers are considerably higher than official estimates. “Between 1995 and 2003, the official tally of Mexicans has climbed 56 percent, and median weekly wage has increased by 10 percent,” the researchers found. “Yet total remittances jumped 199 percent over the same period. Even considering the declining costs of money transfers, the growth of remittances remains astounding.”

The Border Patrol itself has acknowledged that only one of four border crossers is apprehended.12 Some who succeed in crossing the border are apprehended by federal authorities at their workplace, some are incarcerated and deported, and some return home voluntarily, only to return to the U.S. at a later date. Double counting is possible.

We will never know the exact size of the illegal alien population. What we do know is that the growth of that population accelerates when amnesty or other elements of “comprehensive immigration reform” seem likely to be enacted. On January 9, 2004, President Bush proposed a guest worker program — a thinly veiled amnesty for illegal aliens. By June, 2004, U.S. Border Patrol official statistics revealed that there had been 135,468 apprehensions along the Southwest border during April 2004, an 80 percent increase when compared to April 2003. A May 2004 New York Times article stated that after a 4-year drop, apprehensions along the southern border were up 30 percent over 2003 levels.

Similarly, the 1986 Reagan amnesty exacerbated the illegal immigration problem.The 3 million amnesty recipients were scarcely through the legalization process when, by 1992, the illegal foreign-born population was back up to 3.9 million. It doubled again by 2000. Over that same period legal immigrant admissions soared as amnestied illegals brought in their family members.13

When the Reagan amnesty was first announced, the government estimated that about 1 million illegal immigrants would be eligible. The number turned out to be 3 million. Could amnesty for today’s 11 million turn out to be 33 million? Stay tuned.


1. Department of Homeland Security, Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2012, March 2013. Figure 1.

2. Linda Qiu and Amy Sherman, “Donald Trump Reports Pants on Fire Claim about 30 million illegal immigrants ,” Politifact, September 1, 2016.

3. William Campenni, “You Only Think You Know How Many Illegal Immigrants Live in the U.S.” The Daily Signal, December 27, 2015.

4. Nancy Bolton, “The Challenge of Accurately Estimating the Population of Illegal Immigrants,” The Social Contract, Summer 2007.

5. Department of Homeland Security , Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2012, March 2013. Table 2.

6. Ibid., page 1.

7. Department of Homeland Security , 2014 Yearbook of Immigration Statistics, Table 35.

8. DHS, Annual Performance Report, FY 2015-2017, Appendix A, p.64.

9. Terrence P. Jeffrey, “DHS Goal: 19% of Those Detected Illegally Crossing Border into U.S. Will Get Away,” CNS News, April 11, 2016.

10. Brendan Kirby, “Border Crisis: Illegal Crossings May Be Far Higher Than Official Numbers,” LifeZette, October 10, 2016.

11. Robert Justich and Betty Ng , The Underground Labor Force is Rising to the Surface, Bear Stearns, January 3, 2005.

12. Fred Elbel, “How Many Illegal Aliens Are in the U.S.? ,” The Social Contract, Summer 2007.

13. James R. Edwards, Two Sides of the Same Coin: The Connection Between Legal and Illegal Immigration, Center for Immigration Studies,
February 2006

About the author

Edwin S. Rubenstein, a regular contributor to The Social Contract, is president of ESR Research, economic consultants. As a journalist, Mr. Rubenstein was a contributing editor at Forbes and economics editor at National Review, where his “Right Data”column was featured for more than a decade. He is the author of  The Earned Income Tax Credit and Illegal Immigration: A Study in Fraud, Abuse, and Liberal Activism.