NEW YORK (Reuters) - Early test surveys have found that some immigrants are afraid to provide information to U.S. Census workers because of fears about being deported, which could compromise the accuracy of the 2020 census, a government official warned this month.

There has been an “unprecedented ground swell in confidentiality and data-sharing concerns among immigrants or those who live with immigrants,” Mikelyn Meyers, a researcher at the Census Bureau’s Center for Survey Measurement, told a meeting of the bureau’s National Advisory Committee.

The census, which is mandated under the U.S. Constitution and takes place every 10 years, counts every resident in the United States. It is used to determine the allocation by states of seats in the U.S. House of Representatives and to distribute billions of dollars in federal funds to local communities.

Census employees running early test surveys and focus groups reported that immigrants had broken off interviews or given partial or false information about people in their households, Meyers said in her presentation, which is posted online.

“This behavior was an extreme departure from behavior that we have seen in the past,” she reported at the Nov. 2 meeting. “This seems to be related to questions of legal residency or the perception that certain groups are not welcome.”

One person, Meyers said, told government interviewers, “The possibility that the Census could give my information to internal security and immigration could come and arrest me for not having documents terrifies me.”

President Donald Trump campaigned on a promise to crack down on illegal immigration, and soon after taking office in January, he ordered stricter immigration enforcement and banned travelers from several Muslim-majority countries.

Census researchers said immigrants they interviewed spontaneously raised topics like the travel ban and the dissolution of Deferred Action for Childhood Arrivals (DACA), a program that has protected from deportation young immigrants brought to the country illegally as children.

John Thompson, former director of the Census Bureau said such fears could lead to an inaccurate census in which immigrants were undercounted.

“Underrepresentation of the census affects a lot of things,” he said, including the distribution of congressional seats, re-districting and the allocation of billions of dollars in federal funds. Most government surveys that discuss population rely on the census and the ripple effects of inaccuracies would be felt for a decade - until the next full census, he said.

Thompson said one way to address the problem is through more funding for ad campaigns and community outreach to educate people about privacy protections in place.

Michael Cook Sr., a spokesman for the Census Bureau, said that in response to some of the concerns the agency plans to hire 1,000 staff at the local level, an increase of 25 percent compared with the 2010 census.

“These partnership staff, they work and are actually hired at the local level to engage with the communities that we are trying to reach and dispel those myths,” Cook said on Thursday. “They help explain that the census is easy, safe and important.”

DISTRUST

Adding to the complications, the 2020 census will be taking place during a presidential election campaign, said the acting deputy director of the bureau, Enrique Lamas, at the November event.

“If it is anything like some of the election jargon and some of the things that were happening in 2016, it’s going to be a very difficult time to hold a census,” Lamas said.

Trump has promised to expel people living in the country illegally. In the first six months of this year, arrests by U.S. Immigration and Customs Enforcement jumped nearly 40 percent compared with the same period last year.

Some community organizations have told immigrants to not open the door to government officials unless they come with a warrant.

One Census Bureau interviewer said a respondent got up and left her alone in his apartment when she started asking citizenship-related questions.

Another described at the meeting what happened when she approached a cluster of mobile homes where a group of Hispanics lived: “I left the information on the door. I could hear them inside. I did two more interviews, and when I came back, they were moving ... (out of their home) because they were afraid of being deported.”

Even immigrants in the country legally expressed some anxiety to researchers. One respondent in an Arabic-language focus group said Arabs in particular were likely to be “scared when they see a government interviewer at their doorsteps.”

(For the U.S. Census presentation, click here)

(For the U.S. Census memo click here)