Once the Trump administration ends its count for the 2020 census early Friday morning, advocates and even former Census Bureau directors fear the administration won’t take the time to correct what could be the most inaccurate count in decades.

Congress could still pass legislation to extend the Census Bureau’s deadline for delivering apportionment results. The House has already passed such a proposal, which has bipartisan support. But that would mean getting President Donald Trump to give up the goal of controlling the results used to reallocate congressional seats regardless of who wins the general election next month.

The administration pushed to end the count as soon as possible — which the Supreme Court allowed in a ruling Tuesday — to meet a year-end deadline to deliver apportionment results. That would allow Trump to pursue his plans to exclude undocumented immigrants from the apportionment process, assuming the administration wins a pending Supreme Court battle on that issue.

[Trump signs memo to exclude undocumented immigrants from census]

In the meantime, local census advocates like Charyl Kary of the Standing Rock Sioux Tribe in Montana expressed concern that ending the count early will hurt her state. During a call Thursday organized by Common Cause, Kary noted that the pandemic had already put a damper on efforts to count difficult-to- reach populations including Native Americans on reservations.

“Unfortunately, we had to sit idle for many weeks. And so what I see now is that there’s no logical, rational reason for us not to extend the census,” Kary said.

Montana is one of seven states that demographers project could gain another congressional seat this decade, but the early end to the census now puts that in doubt. Montana, along with several other states in the mix to gain or lose seats, fell behind other parts of the country in the last few weeks of the count.

Census Bureau officials said they have counted 99.9 percent of households throughout the country, and argued surges of staff in many areas have helped make up for the shortened schedule. The agency intends to end the count at midnight Thursday in Hawaii, close the online response portal and stop accepting responses postmarked after Thursday.

But some areas still lag behind, such as the office covering the area around Shreveport, La., where more than 10 percent of households have not been counted as of Thursday, or Window Rock, Ariz., which includes much of the Navajo reservation and where about 4 percent of households remain uncounted.

That means those areas will be calculated through less accurate administrative records and statistical methods, said former Census Bureau Director John Thompson. Even to get to the 99.9 percent number, the agency increased proxy interviews — speaking to a neighbor or landlord — that are less accurate than when someone actually fills out the form.

“I don’t think we are going to be as accurate as 2010, that is why the Bureau needs to put more data out,” Thompson said.

Worries over undercounts

In the 2010 count, the Census Bureau overcounted white residents and homeowners and missed hundreds of thousands of people from minority groups, particularly Native Americans on reservations.

The National Congress of American Indians said the shortened count will result in an undercount of “historic proportions” and that the Supreme Court decision “condemns Indian Country to a loss of political representation and its fair share of resources for the next decade.”

Rob Santos, president-elect of the American Statistical Association, said in a statement that “an early ending to the 2020 census data collection hurts our nation, our democracy, and especially the hard-to-count communities of color.”

The group has produced a set of quality measures they want the Census Bureau to publicize so that experts can assess whether census results are useful at all.

In addition to congressional apportionment, census results are used to draw legislative maps, guide $1.5 trillion in federal spending annually and in thousands of business decisions.

Democrats in Congress criticized the Supreme Court decision as well as the agency’s effort to shorten the count. House Oversight and Reform Chairwoman Carolyn B. Maloney, D-N.Y., has for months backed an extension of the agency’s Dec. 31 deadline so the administration would not sacrifice accuracy.

“Under the Constitution, the federal government must conduct a complete and accurate Census, and this duty should not be trumped by adherence to a statutory deadline that never envisioned a once-in-a-generation pandemic and that experts have warned is impossible to meet without compromising the integrity of the Census,” Maloney said in a statement.

After months of delay due to the coronavirus pandemic, the Census Bureau had planned to keep counting through the end of October and take until April to tabulate the data for apportionment. As a result, the agency originally requested that Congress pass legislation to extend a statutory Dec. 31 deadline by 120 days so the agency could deliver apportionment data to the president by the end of next April and detailed legislative mapmaking data to states by the end of next July.

That schedule changed shortly after Trump signed a memorandum to exclude undocumented immigrants from apportionment. Trump signed the memo in July, but that effort has since been halted amid a separate Supreme Court battle.

In August, the Census Bureau announced it would stop in-person counting efforts by Sept. 30 so it could deliver the apportionment totals to Trump by the end of the year.

Advocates have cited the agency’s own experts who said the shortened count will be less accurate. For months, before the administration shortened the deadline, agency officials said they had “passed the point” where they could deliver accurate apportionment results by the end of the year.

After changing the schedule — and after the National Urban League and others took the agency to court — administration officials argued they could produce accurate numbers. But a California federal judge, and later the 9th Circuit Court, found the agency could not ignore accuracy concerns to meet the Dec. 31 deadline, and ordered the count to continue.

That changed Tuesday when the Supreme Court allowed the administration to wind down the count.

Now the agency will have to scramble to properly tabulate and check the numbers in the apportionment count before delivering them to the White House at the end of the year. Thompson said that because of the shortened timeframe, there’s a larger chance that computer errors could go undetected.

“If you don’t count someone there is an undercount, you know that you missed someone, but with a computer error you really don’t know what it is going to do,” he said.

Thompson and other experts have said that giving the agency more time for those administrative records checks could help with accuracy, even though the in-person count was cut short.

The House passed legislation to extend the deadline as part of broader pandemic relief legislation. Several other bills have bipartisan support and would extend the census’ deadline, but have not advanced.

The White House has remained opposed to an extension, even referring to it as a “poison pill” in negotiations over a temporary spending package.