U.S. Border Patrol personnel take illegal immigrants from Honduras into custody in Falfurrias, Texas, June 19, 2018. (Adrees Latif/Reuters)

A new Yale study has concluded that the population of undocumented immigrants in the U.S. is close to double the generally accepted estimate.

The population of undocumented immigrants is widely thought to be around 11.3 million. But the study, which was conducted by three Yale-affiliated researchers, indicates that the total may be more than 22 million. Even the authors were surprised by their findings.


“Our original idea was just to do a sanity check on the existing number,” said one of the study’s authors, Edward Kaplan, a professor of operations research at the Yale School of Management. “Instead of a number which was smaller, we got a number that was 50 percent higher. That caused us to scratch our heads.”

“There’s a number that everybody quotes, but when you actually dig down and say, ‘What is it based on?’ You find it’s based on one very specific survey and possibly an approach that has some difficulties. So we went in and just took a very different approach,” said another of the study’s authors, Jonathan Feinstein, a professor of Economics and Management.

To arrive at their estimate, the authors used operational data such as deportations and visa overstays as well as demographic data such as death rates and immigration rates.



“We combined these data using a demographic model that follows a very simple logic,” Kaplan said. “The population today is equal to the initial population plus everyone who came in minus everyone who went out. It’s that simple.”

“The analysis we’ve done can be thought of as estimating the size of a hidden population,” he added. “People who are undocumented immigrants are not walking around with labels on their foreheads. . . . There are very few numbers we can point to and say, ‘This is carved in stone.'”

The researchers said their goal in crunching the numbers was not a political one.

“We wouldn’t want people to walk away from this research thinking that suddenly there’s a large influx happening now,” Feinstein commented. “It’s really something that happened in the past and maybe was not properly counted or documented.”

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