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Undocumented population is twice as large as previously thought, researchers say

Demonstrators outside the Trump International Hotel in Washington protest the separation of families and criminalization of undocumented immigrants.Astrid Riecken For The Washington Post

The number of undocumented immigrants in the United States may be nearly two times greater than the most widely used estimates show, according to new findings from researchers at the Massachusetts Institute of Technology and Yale University.

Approximately 22.1 million undocumented immigrants are currently living in the United States, according to a new study published Friday. Most previous estimates put the population of undocumented immigrants living in the United States at about 11.3 million, according to a press release from the MIT Sloan School of Management.

The discrepancy is indicative of the challenges that researchers like Mohammad Fazel-Zarandi of MIT, and Edward Kaplan and Jonathan Feinstein of Yale, face when looking for data on a group of people who are so difficult to track, Fazel-Zarandi said.


Previously, researchers have used surveys to estimate the size of the undocumented population, but Fazel-Zarandi said he and his team wanted to try a different approach.

“It’s difficult to locate these individuals, and when you locate them, they might have incentive to provide inaccurate responses to questions,” Fazel-Zarandi said.

The researchers instead used demographic and mathematical models to more accurately gauge the size of the hidden population of undocumented immigrants. They based their research largely on operational statistics about deportations, visa overstays, and border apprehensions, as well as demographic data that provided information about statistics like mortality rates and emigration rates.

This latest approximation could present new implications for the ongoing national debate over policies affecting the undocumented population, Fazel-Zarandi said.

Last September, US Attorney General Jeff Sessions announced plans to rescind the Deferred Action for Childhood Arrivals program. After widespread uproar from DACA supporters, the program was extended.

Earlier this year, the Trump administration tried separating undocumented children from their parents at the border in an effort to discourage new immigrants from entering the country illegally. Trump was forced to reverse course after a public outcry against the policy, which resulted in thousands of separations.


“Our goal was not to do anything political or policy-oriented; it was just to provide a better number, so that policy makers can debate over policies using it,” Fazel-Zarandi said. “The way you have to make policies is with the best information and correct facts. This number will allow policy makers to rethink what they were doing.”

Andres Picon can be reached at andres.picon@globe.com. Follow him on Twitter at @andpicon.