DETROIT (AP) — Detroit sued the U.S. Census Bureau on Tuesday over population estimates from last year that show it lost an additional 7,100 residents, opening another front against the agency in a battle over how the city’s people have been counted in the past two years.

Mayor Mike Duggan told reporters that the city wants the Census Bureau to reveal how it produced its population loss estimates for Detroit. Duggan claimed the bureau was going against its own policy by refusing to divulge to Detroit the way the estimates for the city were calculated and not allowing challenges this year.

The lawsuit appears to be the first litigation to challenge population results since the release of 2020 census data, which traditionally has formed the foundation of the annual population estimates.

The Census Bureau’s refusal this year to consider evidence that the 2021 population estimates were wrong perpetuates racial inequality and threatens the city’s reputation, Detroit said in its lawsuit.

“The Bureau’s failure to consider evidence of its inaccurate 2021 estimate costs the City and its residents millions of dollars of funding to which they are entitled while threatening the City’s historic turnaround by advancing the narrative that Detroit is losing population,” the lawsuit said.

The Census Bureau said in an emailed statement that it doesn’t comment on litigation.

The bureau two years ago temporarily suspended its program allowing local governments to challenge their population estimates so more resources could be devoted to the execution of the once-a-decade census. The program isn’t expected to resume until next year.

Detroit’s lawsuit follows the city’s appeal of the 2020 census data that showed Detroit with 639,111 residents, while estimates from 2019 put the city’s population at 670,052 residents.

Undercounts from the census and population estimates could cost Detroit tens of millions of dollars in federal funding over the next decade. Over the past decade or so, the city has received around $3.5 billion in annual federal funding tied to census figures.

“We have absolutely no idea what formula they could have possibly used,” Duggan said Tuesday. “We don’t know what formula they used because they won’t tell us.”

Duggan said 14 new apartment buildings opened in Detroit last year. DTE Energy has said 7,544 new utility accounts have been added, while the Detroit Water and Sewerage Department said new service has been added to 6,964 housing units, he added.

The U.S. Postal Service also has said it is delivering mail to 4,475 more residences in the city, according to Duggan.

“It’s now clear the data coming out of the U.S. Census Bureau is completely divorced from reality,” he said. “We’re drawing a line in the sand, and we’re going to try to force accuracy out of these guys one way or the other. “

“I think what the formula would show — it would show the error in their calculations, but if we get a formula that turns out they’re right, we’ll admit they’re right,” Duggan added.

Because of delays in releasing the 2020 census numbers, the Census Bureau broke with tradition and didn’t rely only on census figures for creating the foundation of its 2021 estimates of the U.S. population. Instead, statisticians “blended” the 2020 census numbers with other data sets to form the base of the annual population estimates used to help distribute $1.5 trillion in federal funding each year and measure annual population change through 2030.

Detroit is among several large cities to file a challenge of their figures from the 2020 census, following a national head count in which the Census Bureau acknowledged that a higher percentage of African Americans and Hispanics were undercounted than the previous decade. About 77% of Detroit’s residents are African American, and Hispanics make up almost 8% of the population.

Leaders of Michigan’s largest city had questioned the results of the 2020 census since December 2021, when they released a report suggesting that more than 8% of the occupied homes in 10 Detroit neighborhoods may have been undercounted.

Duggan has said in a letter to the Census Bureau that insufficient resources and not enough census takers were devoted to the count in Detroit, resulting in an undercount of unoccupied homes that could amount to tens of thousands of residents being overlooked.

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Schneider reported from Orlando, Florida.

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