WASHINGTON — A federal judge barred the Trump administration on Friday from ending the 2020 census a month early, the latest twist in years of political and legal warfare over perhaps the most contested population count in a century.
In U.S. District Court for the Northern District of California, Judge Lucy H. Koh issued a preliminary injunction preventing the administration from winding down the count by Sept. 30, a month before the scheduled completion date of Oct. 31. She also barred officials from delivering completed population data to the White House on Dec. 31 rather than the April 2021 delivery date that had previously been set out.
The judge had temporarily stayed the early completion of the census count on Sept. 5 pending a hearing held on Tuesday.
The ruling came after evidence filed this week showed that top Census Bureau officials believed ending the head count early would seriously endanger its accuracy.
In one July email, the head of census field operations, Timothy P. Olson Jr., called it “ludicrous” to think a curtailed population count would succeed. A second internal document drafted in late July said a shortened census would have “fatal data flaws that are unacceptable for a constitutionally mandated national activity.”
The administration ordered the speedup anyway. Critics immediately said it would lead to drastic undercounts, particularly for low-income areas and communities of color, which are least likely to respond to the census.
The Trump administration had argued that it needed to end census-taking early to begin processing state-by-state population data or it would miss a statutory Dec. 31 deadline for sending population figures to President Trump. .
That was widely seen as an effort to ensure that Mr. Trump — and not Joseph R. Biden Jr., should he win the presidential election — controls census figures that will be used next year to reallocate seats in the House of Representatives and draw thousands of political boundaries nationwide.
Mr. Trump had formally asked Congress this spring to extend the December deadline to April 2021, citing delays in the census caused by the coronavirus pandemic. The Democratic-controlled House registered its approval, but the Republican-controlled Senate has not acted on the request, leaving the administration leeway to order the shorter count.
Mr. Trump ordered in July that unauthorized immigrants be removed from population totals used for reapportionment, a move that would create a whiter, less urban and presumably more Republican population base for distributing House seats.
His directive has already been rejected as illegal by a federal court, a ruling the Justice Department said it will appeal.
In a 78 page opinion, Judge Koh said that a mound of internal Commerce Department and Census Bureau documents showed that both agencies knew the earlier deadlines could not be met without a high risk of creating a flawed population count. They also knew that the pandemic gave them ample legal justification for missing the December deadline for delivering data to the president, she wrote.
Yet their only explanation for shortening the census, she said, was a two-page press release issued on Aug 3 that said the December deadline had to be met.
“The Aug. 3 press release never explains why defendants are ‘required by law’ to follow a statutory deadline that would sacrifice constitutionally and statutorily required interests in accuracy,” Judge Koh wrote.
The Commerce Department, which oversees the Census Bureau, did not immediately react to the ruling.
Most others with a stake in the accuracy of the count — cities and states, businesses, advocates of underrepresented minorities — said giving the bureau more time was essential to ensuring that the count be even reasonably accurate.
“Today’s decision is a victory for data quality,” said the incoming president of the American Statistical Association, Rob Santos. “It’s vitally important to give the hard-working census employees the time to ensure as fair and accurate a census as possible.”
Judge Koh’s order offered some breathing room for a Census Bureau that has been struggling to manage what was supposed to be the most accurate population count ever, conducted largely over the internet and aided by an army of census takers equipped with iPhones.
Instead, this year’s census has been a star-crossed exercise, pushed far behind schedule by the coronavirus pandemic, stymied by clumsy software and so mired in Republican political strategizing that even former directors of the Census Bureau have called the entire count into question.
Even this week, the government’s sole witness in the lawsuit, Albert E. Fontenot Jr., the associate director for decennial census programs, said in a deposition that the pandemic, western wildfires and major storms in the South posed “significant risks to complete all states by September 30.”
Despite those hurdles, the Census Bureau says it has finished counting more than 96 percent of the nation’s households, theoretically placing it in reach of its stated goal of 99 percent by the end of the month. But whether that can be done — or done accurately — remains in great doubt.
Nationwide, the completion rate varies widely, with four states above the 99 percent goal. Six states remain below 90 percent and are considered poor candidates to be completed by month’s end.
Beyond that, the reported completion rates are an unreliable barometer of the census’s accuracy because a household can be deemed counted in many ways, with wildly varying precision. The rates do not show the share of households that have been counted by highly reliable methods like internet or in-person interviews, versus by dicier means like asking a neighbor or relying on personal information from a database.
On Monday, the inspector general of the Commerce Department said the compressed schedule threatened the reliability of both the head count and the data processing and error checks that follow it.
The report quoted unnamed senior census officials as saying the early deadlines have forced shortcuts in reviews of data and other quality-assurance steps that ensure a reliable population count.
The report also said the Census Bureau was forced to shave a month off its head count because it had been ordered by unnamed higher-ups in the Trump administration to deliver data to the White House by Dec. 31, and could devise no other way to meet that goal.
At least one senior Census Bureau official appeared convinced this summer that even a shortened count would not free up sufficient time to deliver a credible count.
“Any thinking person who would believe we can deliver apportionment by 12/31,” Mr. Olson, the executive running daily census operations, wrote in a July 23 email, “has either a mental deficiency or a political motivation.”
