Years of preparation for the 2020 census in Minnesota paid off with the highest self-response rate in the nation. But as the operation closes out Friday, questions remain about the accuracy of the data, and it will take months to determine whether Minnesota will lose a congressional seat to a faster-growing state.

The census has been plagued by both political controversy and a pandemic that dramatically shifted the timeline of the once-in-a-decade count. Ultimately, three-quarters of Minnesota households responded themselves — vs. through a census taker — the highest proportion of any state.

That's good news for Minnesota, because self-responses are typically more accurate than those collected during the follow-up operation. The U.S. Census Bureau says 99.9% of known households have now been counted in each state, but that includes information gleaned through neighbors, landlords and administrative records in addition to direct interviews.

The census is often called the country's largest mobilizing effort outside of going to war. Fittingly, Minneapolis encouraged its "census warriors" to finish strong in an e-mail Thursday. Minnesotans formed more than 350 "complete count committees" to raise awareness about the count in every corner of the state. Thousands of paid workers fanned out across the state searching for people who hadn't responded.

The data inform how billions of federal dollars are spent, in addition to how political boundaries are redrawn.

"There were a lot of challenges that we didn't expect with this census, first and foremost the COVID-19 pandemic, which set the census timeline back a number of months over the summer," said Sam Fettig, the bureau's Minnesota partnership coordinator. "But overall [I'm] very pleased with where we ended up."

A coalition of advocacy groups tried to block the Trump administration from ending counting operations earlier than Oct. 31, but the U.S. Supreme Court ruled this week that counting could conclude by the end of Thursday Hawaii time — roughly 5 a.m. in Minnesota.

Minnesota is at risk of losing a congressional seat based on the census, which is likely to be affected by the outcome of another looming court case. The Trump administration wants to exclude immigrants living in the country illegally from counts that determine each state's congressional seats, a departure from longstanding practice.

A number of states and cities, including Minnesota, argued in a lawsuit that this violates the Constitution. The Supreme Court is expected to hear that case later this year.

The American Statistical Association is pushing for more transparency about how often the census counted people through proxies or records — vs. interviewing them or receiving their forms.

"There's always going to be some error in there," said Susan Brower, state demographer. "But just because there were so many disruptions this time around, there still remain concerns that the quality isn't there like it was in 2010."

Fettig said that the Bureau typically makes up to six attempts to contact each household in person or over the phone. Only after those efforts are exhausted does it seek out someone else — like a neighbor or landlord — with firsthand knowledge of at least how many people live in the household. Administrative records like Postal Service data are used as a last resort, he said.

Brower said she is also concerned about incomplete data from historically undercounted communities, based on maps showing where fewer people self-responded. That includes college students, renters, people of color, immigrants, rural communities, Indigenous communities and low-income people.

"We know that under normal circumstances these are difficult populations to count," Brower said. "And this time around there were abnormal and very disruptive circumstances and so … I expect that they were even harder to count."

She added that U.S. Census Bureau's shifting deadline for the end of the survey hasn't helped it plan how to best use its time.

Minnesotans should be proud of having the highest self-response rate in the nation, said Xiongpao "Xp" Lee, who oversees the census for the Minnesota Council on Foundations.

"The numbers really give us a lot of optimism in terms of really having an accurate-as-possible count for 2020," Lee said. "And everything that that means in terms of being able to get the most out of our [congressional seat allocation], in terms of federal dollars."

Lee said some organizations involved in the census will be pivoting to work next year on redistricting, the redrawing of boundaries for everything from congressional seats to city council wards.

Eric Roper • 612-673-1732

Twitter: @StribRoper