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By MIKE SCHNEIDER Associated Press

ORLANDO, Fla. (AP) Legal wrangling has surrounded the U.S. census count for decades, culminating in this year s fight over adding a citizenship question.

Most challenges have centered on correcting mistakes counting underrepresented populations such as minorities in the official census, which determines how many congressional seats each state gets and how hundreds of billions of federal dollars are distributed.

The census is a bureaucratic instrument which is supposed to function neutrally, but numbers are always political in any kind of refashioning of the population for political purposes, said Sarah Igo, a history professor at Vanderbilt University.

For the first half of the 20th century, the federal courts deliberately avoided cases involving reapportionment of congressional seats, according to historian Margo Anderson, who wrote the book The American Census: A Social History. Judges largely left such decisions in the hands of state legislatures.

An envelope contains a 2018 census letter mailed to a U.S. resident as part of the nation s only test run of the 2020 Census. (AP Photo/Michelle R. Smith, File)

That changed in 1962 when the U.S. Supreme Court took up a Tennessee case and issued a landmark ruling that federal courts could hear redistricting cases. The case produced the one person, one vote standard for ensuring fair representation in legislative redistricting.

By the early 1960s, improvements in survey techniques and data processing allowed the U.S. Census Bureau to see which populations were being undercounted, which could affect whether they were accurately represented in drawing congressional districts or getting their fair share of federal funds.

The capacity to measure census accuracy, to know whether you are doing a good job or not, really dates to the second half of the 20th century, Anderson said in an interview Tuesday. Statistical methodology developed to a point where you could have more than an anecdotal sense of inaccuracies.

Combined with the Supreme Court s new standard, those technical improvements opened the door for a series of federal lawsuits after the 1970 census claiming non-English speakers in urban areas were being overlooked.

Those lawsuits were dismissed, but the fight over how to count accurately was just warming up....