Undocumented Immigrants In The U.S. Drop To Lowest Level In 12 Years

Despite that, poverty and rampant violence continue to fuel migration from Central America. Thousands of people primarily from Honduras make up the bulk of the migrant caravan that's been trekking towards the U.S. border, prompting threats of a crackdown from President Trump. 

Undocumented immigrants from Asia accounted for 1.3 million people living in the United States in 2016, the third-largest unauthorized group after Mexico and Central America, according to Pew. Unlike their counterparts from Mexico and Central America, these immigrants are unauthorized due to expired visas rather than illegal border crossings, according to the Migration Policy Institute.

"A lot of that has to do with visa overstays," said Randy Capps, the director of research for U.S. programs at the institute, in a telephone interview with CBS News on Wednesday. "It's become a larger and larger source of the unauthorized population and it's likely a majority of the new unauthorized population as opposed to border crossings."

The Migration Policy Institute estimates the number of undocumented immigrants living in the United States in 2016 to be 11.3 million, about half a million more than Pew's study. The group uses proprietary methodology to determine legal status within the most recent U.S. Census Bureau's American Community Survey results.

At Pew, the number of unauthorized immigrants living in the United States was determined by using the same Census data and then ascribing legal status through a combination of other demographic data, according to group's methodology.

In the 2020 Census, the Trump administration wants to explicitly ask households whether or not they are living in the United States legally, the first time the question has appeared in 70 years. However, the question is being challenged in court. Depending on the outcome, it could make it even more difficult to accurately gauge the number of undocumented immigrants in the future.

"If you combine the intent of that question, which is clearly political, with politics and immigration, you're going to find yourself in an atmosphere where people don't want to answer," Capps said.

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