WASHINGTON — The 2020 census undercounted the population of six states and overcounted residents in eight others, the Census Bureau said on Thursday, a finding that highlighted the difficulties of conducting the most star-crossed population count in living memory.
The conclusions come from a survey of 161,000 housing units conducted after the census was completed, a standard procedure after each once-in-a-decade head count of the U.S. population. The results showed that six states — Arkansas, Tennessee, Mississippi, Florida, Illinois and Texas — likely have a larger population than was officially counted.
Eight states likely have fewer residents than were recorded, the survey found: Hawaii, Delaware, Rhode Island, Minnesota, New York, Utah, Massachusetts and Ohio. The count in the remaining 36 states and the District of Columbia was basically accurate, the bureau said.
The results were markedly worse than in the 2010 census, in which none of the states had a statistically significant overcount or undercount, the agency found. But they were not unlike the conclusions from the 2000 census post-mortem, which found overcounts in 21 states and an undercount in the District of Columbia.
John H. Thompson, the director of the Census Bureau from 2013 to 2017, said in an interview that he was not surprised by the variations, given the problems that dogged the 2020 census. “All censuses have overcounts and undercounts,” he said. “That does not preclude using the results.”
The Census Bureau said in March that the same survey had found undercounts of Black and Hispanic people, and overcounts of white people and people of Asian descent in the national population totals. Overcounts of white people and undercounts of other racial and ethnic groups have been a persistent problem in past censuses.
The survey was not broad enough to offer reliable estimates of those discrepancies on a state-by-state basis, the bureau said.
The post-mortem will not change the official state-by-state results of the census, which said that 331,459,281 people were living in the United States in 2020. Nor will it alter the allotment of seats in the House of Representatives or in state and local political districts, even though its findings arguably could have affected those decisions.
The Supreme Court has barred the use of surveys in apportioning seats in the House, and in any case, the latest survey has a large margin of error that makes its conclusions more like educated guesses than solid findings.
But it does offer insights into where the census likely fell short, and perhaps why. Geographically, five of the six states with population undercounts were in the Deep South, while six of the eight states that were most overcounted are in the North, and particularly the Northeast.
Experts say there are many possible explanations for the disparities in the count, including the Covid-19 pandemic, which roared across the country as the census was being conducted.
In particular, the pandemic made many people reluctant to open their doors to census-takers at a time when the bureau was trying to get information about tens of millions of people who had yet to be tallied on census forms.
This is a developing story. Check back for updates.