How the Tally of Illegal Immigrants Adds Up, and Why It Matters
Consistent estimates around 11 million allow policy makers baseline around which to plan, budget
Illegal immigrants living in the U.S. have obvious reasons to want to avoid detection, even as the government and others try to figure out how many are here.
The Department of Homeland Security in its official tally says 11.4 million unauthorized immigrants live here. The Pew Research Center, a nonpartisan think tank in Washington, D.C., puts the figure at around 11.2 million. And the Center for Migration Studies, a nonprofit based in New York, calculates that it’s just over 11 million.
Keeping track is important for a variety of reasons. Schools, for example, must enroll K-12 students regardless of immigration status. Unauthorized immigrants without insurance will likely visit emergency rooms for health care, the cost covered in part by Medicaid. And changes in the population may influence border enforcement and other policies.
President Barack Obama focused attention on the issues in November when he unveiled a series of executive actions that would protect up to 5 million illegal immigrants from deportation. The move was temporarily halted by a federal judge in response to a lawsuit questioning the president’s authority, so for now, we don’t know whether the estimated number of beneficiaries would have proved accurate.
But it raises the question: How do demographers count a population that doesn’t wish to be found?
Techniques for calculating the number of illegal immigrants have been around for at least 30 years. Traditionally, the calculation involves something called residual methodology—or, as most of us would think of it: subtraction.
“The process is both simple and complicated,” said Jeffrey S. Passel, a demographer at the Pew Research Center who previously worked for the U.S. Census Bureau. “We determine how many immigrants are in the country legally, and we subtract that from how many are in the country total.”
Until the 1980s, conventional wisdom held that illegal immigrants weren’t represented in government population surveys. But a supplement to the Current Population Survey in the early 1980s asked residents why they didn’t vote, and the number who responded by saying they weren’t citizens exceeded the estimated number of legal immigrants in the same area.
“We discovered nonauthorized immigrants are in the data,” said Robert Warren, a visiting fellow at the Center for Migration Studies who previously was also a demographer at the Census Bureau. “That changed things.”
Using the residual technique, which Messrs. Warren and Passel pioneered, researchers assume all foreign-born residents who entered the U.S. before 1980 or 1981 (depending on who’s doing the math) are legal. That is because immigrants who came in illegally before then were offered amnesty through the Immigration Reform and Control Act of 1986.
Using that cutoff as a starting point, researchers determine the total number of foreign-born people who entered the country afterward from Census data—and subtract the number who entered the country legally, including permanent residents with green cards issued by the U.S. Citizenship and Immigration Services, refugees, individuals granted asylum, and workers and students with temporary visas.
To further refine the figures, the researchers estimate how many immigrants left the country; they apply standard mortality rates to deduce how many died; they calculate a margin of error due to sampling; and they adjust for undercounting in the Census.
The Census Bureau has measurements of undercount that show consistent patterns by sex, age and race, and the researchers use these patterns to correct their figures.
Men are more likely to be missed than women. The highest undercount rates are found in young adults in their 20s and 30s. And minorities are more likely to be missed than whites. Among immigrants, people who are naturalized U.S. citizens are less likely to be missed in government surveys, followed by legal immigrants, follow by unauthorized immigrants.
Steven Camarota, director of research for the Center for Immigration Studies, which believes in strict enforcement of immigration laws, said there are “question marks” about the accuracy of the estimates because of the inherent challenges in counting an undocumented population. But the figures most likely are in the ballpark, he said.
“It could be 12 million or 13 million,” Mr. Camarota said. “It doesn’t seem like it could be 15 million or 20 million.” If the estimates were dramatically off, Mr. Camarota said, it would be reflected in births and school enrollment figures, which he noted are not “out of whack” with the estimates.
To help verify his own figures, Mr. Passel cross-references U.S. data with figures from the Mexico census. More than half of the unauthorized immigrants in the U.S. are from Mexico—or around 5.9 million, by Mr. Passel’s count. It is by far the largest source of illegal immigrants in the U.S.
To test that figure, for example, he compares how many children age 4 and younger were born in Mexico 20 years ago with how many Mexicans age 20-24 live there now. The numbers should be roughly equal. If there are substantially fewer young adults, it suggests the number of immigrants in that age group who have entered the U.S.
The uniformity of the estimates over time and between agencies gives the researchers confidence their estimates are on target.
Still, it is impossible to know how close the estimates come to the real number.
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Originally Posted by Zippyjuan
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