San Francisco and San Jose are among 20 metropolitan regions with the largest populations of undocumented residents in the United States, according to a first-of-its-kind report by the Pew Research Center.

The report highlights a population at the center of a heated debate, as President Donald Trump looks to double down on deportations.

There are an estimated 240,000 undocumented residents — about 5.3 percent of the region’s total population — living in the metropolitan area of San Francisco, Oakland and Hayward, according to the report.

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Opinion: Christians must fight Trump attempt to monopolize faith Meanwhile in the South Bay, there are an estimated 120,000 undocumented residents — about 6.5 percent of the total population — living in the metropolitan area of San Jose, Sunnyvale and Santa Clara, the report said.

It’s the first time Pew Research has published estimates of undocumented residents by metropolitan area and city. The report, released Thursday, used 2014 Census data to analyze the population of undocumented residents and is part of an ongoing effort by Pew to study a group that is often difficult to track down.

The research center used figures from the Census Bureau’s American Community Survey, which tracks all immigrants — legal and illegal. The survey asks participants where they were born and whether they are U.S. citizens, but does not explicitly ask if they’re here illegally.

The country’s lawful immigrant population is estimated using data from the Department of Homeland Security’s Office of Immigration Statistics. The number of legal immigrants is then subtracted from the total number of immigrants in the U.S., and the difference reveals the country’s undocumented population, researchers said.

“This lets us look at specific areas in ways that we can’t do with state data,” said Jeff Passel, a senior demographer for Pew and co-author of the report.

Together, the 20 metropolitan areas are home to an estimated 6.8 million undocumented residents or about 61 percent of the country’s 11 million undocumented residents.

Five of the areas highlighted in the report are in California: Los Angeles, Riverside-San Bernardino, San Francisco, San Diego and San Jose. New York had the highest number in the country, with an estimated 1.2 million undocumented residents. Los Angeles had 1 million but high numbers were also reported in the regions surrounding Atlanta, Miami, Dallas and Chicago.

“I think what people often forget is that San Jose is the 10th largest city in the country, and as such, it is a major metropolitan center. That has a lot to do with what our demographics look like,” said Julia Curry, a professor of Mexican-American Studies who has helped established resources for undocumented immigrant students at San Jose State.

San Jose has been an extremely diverse region since the mid-1800s, according to Curry, who said immigrants tend to gravitate to areas where there are already established immigrant communities.

The report comes at a time when sanctuary cities and counties across the U.S. stand to lose millions in federal funding for pledging to protect undocumented residents from immigration officials, a promise that has, particularly, pit California against President Donald Trump.

Meanwhile, state officials are moving forward with Senate Bill 54, a bundle of ambitious legislative policies that would protect immigrants who are at risk of deportation. The fast-tracked proposals would prevent local and state police agencies from collecting information about a person’s immigration status and from holding a person for federal agents without a judicial warrant, among other restrictions. Many say the bill, which has to clear two committees before reaching the Senate floor, would turn California into a sanctuary state.

Critics have said the proposal would make it even more difficult for law enforcement officials to apprehend dangerous criminals. Meanwhile, Trump has said California is “out of control” and affirmed that the state remains at risk of losing federal funding because of its stance on immigration.

Joe Guzzardi, spokesman for Californians for Population Stabilization, said the concept of welcoming all immigrants isn’t sustainable and often leads to job shortages and income inequality.

“It’s reached a level in California where people, even immigration advocates, need to stop and focus on what the end game might be, and maybe give a little more voice to how continued waves of illegal immigration and even legal immigration are not very beneficial to the immigrants that are already in the state,” he said.

Pew plans to provide additional estimates of undocumented populations this year using more recent data sets, according to Passel. “Our idea is to put out data that we hope people can use in assessing, formulating and reacting to policies,” he said.