Commerce Secretary Wilbur Ross “has determined that reinstatement of a citizenship question on the 2020 decennial census questionnaire is necessary to provide complete and accurate census block level data,” the statement said.

In a statement released Monday, the Commerce Department, which oversees the Census Bureau, said that including an inquiry about citizenship status would allow the department to accurately measure the portion of the population eligible to vote.

WASHINGTON — The 2020 Census will ask respondents whether they are US citizens, the Commerce Department announced Monday night, agreeing to a Trump administration request with highly charged political and social implications that many officials feared would result in a substantial undercount.


But critics of the change and experts in the Census Bureau itself have said that, amid a fiery immigration debate, the inclusion of a citizenship question could prompt immigrants who are in the country illegally not to respond. That would result in a severe undercount of the population — and, in turn, faulty data for government agencies and outside groups that rely on the census. The effects would also bleed into the redistricting of the House and state legislatures in the next decade.

The Justice Department had requested the change in December, arguing that asking participants about their citizenship status in the decennial census would help enforce Section 2 of the Voting Rights Act, which aims to prevent voting rights violations.

“The Justice Department is committed to free and fair elections for all Americans,” and has sought reinstatement of the citizenship question on the census to fulfill that commitment,” a Justice Department spokesman, Devin M. O’Malley, told The New York Times in February.

The decennial census generally included a citizenship inquiry for more than 100 years through 1950, according to the Commerce Department. And other, smaller population surveys, such as the Current Population Survey and the American Community Survey, continue to ask respondents about it.


But critics dismissed administration officials’ reassurances.

“The census numbers provide the backbone for planning how our communities can grow and thrive in the coming decade,” said Xavier Becerra, California’s attorney general. “What the Trump administration is requesting is not just alarming, it is an unconstitutional attempt to discourage an accurate census count.”

Others argued that an undercount in regions with high immigrant populations would lead not only to unreliable data but also to unfair redistricting, to the benefit of Republicans.

“Adding this question will result in a bad census — deeply flawed population data that will skew public and private sector decisions to ensure equal representation, allocate government resources and anticipate economic growth opportunities — for the next 10 years,” Vanita Gupta, chief executive of the Leadership Conference on Civil and Human Rights and a deputy attorney general in the Obama administration, said in a statement Monday night. “The stakes are too high to allow this. We urge Congress to overturn this error in judgment.”

The announcement of the citizenship question comes at a troublesome time for the Census Bureau: Its top two positions have interim occupants, and it has been forced to skip two of its three trial runs for the 2020 census because of funding shortfalls. If response rates for the census are low, critics worry that the bureau may be unable to adjust the data or deploy enough census takers to low-response communities.


The bureau is required to submit a final list of the 2020 census questions to Congress by the end of March.