The Trump administration proposed major changes Wednesday to the decennial census, calling for the elimination of questions on race, ethnicity and sexual orientation, which it said would bring the questionnaire more in line with the census’ original purpose.
The proposal also calls for dropping illegal immigrants and temporary foreign visitors from the official apportionment count, which is used to apportion the 435 seats in the House of Representatives.
The changes would be among the biggest ever to the main census count, which surveys every household in the country.
Census officials said the proliferation of demographic questions has tainted the survey, causing some people to refuse to respond. The granularity of data now available could make it possible to identify specific census respondents, creating an invasion of their privacy, the bureau said.
“The collection of such data does not, by itself, advance the fundamental, constitutional purpose of the decennial census, which is to conduct an enumeration to ascertain the population count for apportionment,” Commerce Secretary Howard Lutnick said in the proposal, which is scheduled to be published in the Federal Register on Thursday.
That will kick off a 30-day public comment period, and the Commerce Department would then have to ponder changes and finalize the plan before it takes effect.
The question changes would apply only to the short-form questionnaire, which is sent to all households every 10 years.
Other surveys, such as the more thorough American Community Survey, which scrutinizes a rotating subset of homes, could still ask demographic questions.
That information, as well as data held by other government agencies, could fill any gaps that arise from dropping the questions from the short form, the bureau said.
Trump opponents are already lining up against the ideas.
“The administration’s proposal is a flagrant assault on our democracy, designed to manipulate voting maps and dilute the political representation of diverse American communities,” said William Roberts, senior vice president for rights and justice at the liberal-leaning Center for American Progress.
Opponents said the Constitution requires counting all people in the U.S., including illegal immigrants, when it mandates a count of the “whole number of persons in each state.”
The Census Bureau, in the new proposal, said the “whole persons” requirement contains an element of “allegiance” to the country. Illegal immigrants and those here on only temporary status should fall outside that, the bureau argued.
“In particular, the Census Bureau finds merit in the interpretive argument outlined above and has preliminarily determined that, under the best reading of the constitutional mandate, illegal aliens (among others) should not be included in the apportionment count, as they are not true inhabitants, members of the body politic, or persons with a ’usual residence’ in the United States due to their lack of a sufficient tie and allegiance to the United States,” Mr. Lutnick wrote.
Legal permanent residents would still be counted.
Steven Camarota, the research director at the Center for Immigration Studies and a longtime tracker of apportionment figures, said that an estimated 17 million to 18 million people would be considered illegal immigrants or temporary legal visitors.
Removing them could shift a handful of seats among the states, though the change would not be massive.
Figuring out how to exclude migrants from the count could be tricky.
Census officials, in the new proposal, said they think they can use information from other agencies to try to identify illegal immigrants. Failing that, they could also add a new demographic question asking specifically about legal status.
The first Trump administration tried to add a citizenship question to the 2020 census, but the Supreme Court ruled the administration’s justification was pretextual, effectively blocking the question from the 2020 count.
The justices, in a divided ruling, said the Census Bureau has the right to ask about citizenship — and indeed did so in many iterations — but Mr. Trump’s team botched the effort to rush the question into the 2020 count.
In particular, Chief Justice John G. Roberts Jr. said, the administration used a pretext to defend the question, rather than acknowledging the true reasons for it.
Seeking to head off a similar ruling, the new regulatory proposal explains its reasons at length.
The first census in 1790 divided people into categories: free White males 16 and older, free White males younger than 16, free White females, all other free persons and slaves.
From then until 1950, census takers assigned racial classifications. Starting in 1960, as part of a transitional process, people began to select for themselves. Complete self-identification via mail-out forms began in 1970. The survey has not asked about sexual orientation explicitly, but in the 2020 census, it did ask about same-sex spouses or partners.
Dropping those demographic questions “would reduce response burden as well as the risk of disclosure,” Mr. Lutnick said.
The census became a political issue in 2010, amid the rise of the conservative tea party movement, with some adherents refusing to fill out the form in protest of its intrusiveness.
The 2020 census short form asked for the number of people in a household, each person’s name, sex, date of birth, race, ethnicity, relationship to the householder and whether the home was owned or rented. The form also asked for the telephone number of the person who filled it out.
Data from the decennial count serves as the backbone of other surveys, which are often adjusted to match the demographic breakdown of the 10-year count.
Eliminating the demographic questions could affect the other work.
Mr. Camarota said the demographic questions are also used to identify any undercount in the 10-year survey, and that could be trickier without that data.

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