ORLANDO, Fla. -- 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.
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.
Beginning in the 1980s, a slew of lawsuits from Detroit, New York City and New York state tried to compel the Census Bureau to adjust for undercounted minority communities. The adjustment would come from conducting a sample count and then using those results to tweak the final numbers in the decennial count. The courts upheld the federal government's resistance to sampling, with one case reaching the Supreme Court in 1996.
In the 1990s, the Republican-controlled Congress sued the Clinton administration over its plans to conduct sampling for the 2000 census, and the matter went back to the Supreme Court. The high court ruled that the law on how to conduct the census ruled out sampling for allocating congressional seats. But the justices didn't rule on its constitutionality.
After the decision, the Census Bureau considered using the adjusted data for tasks not related to apportionment, like redistricting, but ultimately dropped the idea because of concerns about accuracy, according to the bureau's website.
Since then, Census Bureau directors have agreed to use sampling to measure the count's accuracy but not to change numbers.
Other legal challenges in the 1990s led to court rulings that there could be state-to-state differences in the size of congressional districts and that overseas federal employees could be counted.
Massachusetts had argued that including overseas personnel didn't meet the requirement to count the number of people in each state. But Justice Sandra Day O'Connor wrote for the Supreme Court majority that "assuming that employees temporarily stationed abroad have indeed retained their ties to their home states actually promotes equality."
Utah sued after the 2000 census, claiming a technique for filling in missing data and the omission of overseas missionaries in the count cost it a congressional seat, but a federal court ruled for the Census Bureau.
What makes the current citizenship question litigation unique is how close it's taking place to the 2020 count in spring. The Supreme Court recently blocked the question, at least temporarily, saying the Trump administration's justification "seems to have been contrived." But President Donald Trump has vowed to push forward with it.
"The real issue isn't just the litigation," Anderson said. "It's that we're very late in the game."
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