Commerce Secretary Wilbur Ross said critics’ claim that including a question about citizenship status on the 2020 Census will lead to fewer responses is based more on a gut feeling than actual evidence.

“ The Constitution requires that the Census count all persons, not just citizens, for the purpose of apportioning representation in the House. The Census has nothing to do with voter registration. ”

“No one provided evidence that there are residents who would respond accurately to a decennial census that did not contain a citizenship question but would not respond if it did, although many believed that such residents had to exist,” Ross wrote in a memorandum released late Monday along with his decision.

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“While it is possible this belief is true, there is no information available to determine the number of people who would in fact not respond due to a citizenship question being added, and no one has identified any mechanism for making such a determination,” Ross said.

Ross said two former top Census Bureau officials, one who served during Barack Obama’s presidency and one from the George W. Bush administration, told Commerce Department officials that adding the citizenship question risked lowering the response rate but said there was limited empirical evidence to support this view. Ross did not identify the former officials.

Even if there is some impact on responses, the value of data from the addition of the question outweighs concerns, Ross said. The citizenship question was asked on most decennial Census forms until 1950, and has been asked on the yearly American Community Survey form.

Critics say the question would cause immigrants who are in the country illegally not to respond, for fear that their information would be turned over to the Justice Department or to the Immigration and Customs Enforcement, even though, by law, individual information from the Census cannot be shared with any other agency for 72 years.

Their fears are not totally unfounded. During World War I, the Census turned over to the military the names of men who were of draft age but not registered. During World War II, the Census turned over the names and addresses of some Japanese-Americans to the Secret Service. The law has since been changed to require more privacy.

Fear of deportation could result in an inaccurately low count of the population in the 2020 Census, critics say. The Constitution requires that the Census count all persons, not just citizens, for the purpose of apportioning representation in the House. The Census has nothing to do with voter registration.

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A low count could also lead to less government and private-sector assistance to vulnerable groups and to the places they live.

California Attorney General Xavier Becerra announced he is suing the Trump administration over the decision. He said the inclusion of the question is illegal.

Former U.S. Attorney General Eric Holder also said he would file a suit on behalf of the National Democratic Redistricting Committee. Holder said the citizenship question is not necessary in order to enforce the Voting Rights Act, as current Attorney General Jeff Sessions claimed.

Some commentators told the Commerce Department that the political climate generally and fears that Census responses could be used for law-enforcement purposes would limit cooperation from immigrants.

“The reinstatement of a citizenship question will not decrease the response rate of residents who already decided not to respond,” Ross said.

The commerce secretary said he would place the citizenship question last on the census form to minimize its impact.

However, an internal Commerce Department memo in September 2017 reported that researchers had noticed “a recent increase in respondents spontaneously expressing concerns about confidentiality in some of our pretesting studies conducted in 2017” due to fears of deportation. The memo recommended “systematically collecting data on this phenomenon, and development and pretesting of new messages to avoid increases in nonresponse among hard-to-count populations.”

In the last decennial Census in 2010, it was the right wing, not immigrants, expressing fears about their privacy would be invaded.

Rep. Michelle Bachman of Minnesota, an unsuccessful candidate for the Republican presidential nomination in 2012, boasted that she refused to answer Census questions because she didn’t want the Obama administration to have her information. Conservative pundit Erick Erickson said on his radio show that if a Census worker came to his door asking him to fill out the separate American Community Survey form, he would “pull out my wife’s shotgun.”