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.

In a memorandum explaining his decision, Mr. Ross wrote that he had considered opponents’ arguments about the potential to discourage responses.