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2020 census: Defining the next decade

ASU's Knowledge Exchange for Resilience examines how Arizona performed and how mapping response rates might improve future accuracy

A photo of the 2020 census letter

Photo by Enayet Raheem on Unsplash

November 05, 2020

Amid new challenges posed by COVID-19, states struggled to increase their census self-response rates in 2020. 

Widely considered the most accurate method used in this once-in-a-decade population count, these rates stagnated nationwide around 67% and only reached 64% in Arizona, ranking 32nd nationally. In 2010, the census undercounted an estimated 16 million people nationwide. Assessing the 2020 census, the Urban Institute estimates up to about 100,000 Arizona residents might be missed.

This year census workers had about three months — as opposed to the usual five — to follow up with those who hadn’t already responded online, by phone or by mail. These counts are already less reliable than self-responses, as their accuracy depends upon a resident being home, in addition to being able to understand and willing to respond to the census worker’s questions.

And accuracy matters. Census counts are used to determine Congressional representation, draw local political districts and allocate more than $650 billion of federal funding each year. The Arizona Complete Count Committee estimates that every resident not counted represents an annual loss of $887 in federal funding for education, transportation and social services.

“Certain populations like renters, people of color, young children, rural and Indigenous communities are all typically undercounted,” said Patricia Solis, executive director of Arizona State University's Knowledge Exchange for Resilience. For these populations, an undercount can mean 10 years of underrepresentation and underfunded services.

Although Arizona as a whole exceeded its 2010 self-response rate, the rates varied widely among counties and census tracts.

The 2020 Census Response Rates for Arizona map, developed by the Knowledge Exchange for Resilience with support from Geospatial Research and Solutions and using a data feed from the U.S. Census Bureau, depicts self-response rates for each Arizona census tract. 

Map of 2020 census response rates for Arizona

“We wanted to be able to track in real time what areas of Arizona were having good response rates and which weren’t so that it would enable us to work with community partners in particular areas to encourage their residents to complete the census,” said Lora Phillips, postdoctoral research scholar for the Knowledge Exchange for Resilience. 

The map includes layers depicting response rates from 2010 and 2020 and a layer highlighting which census tracts achieved a rate of 25% or less.

“Looking ahead, it’s going to really benefit us to have in 2030 two previous data points and be adding a third, so we can see trends in certain neighborhoods,” she added. 

“The next step is to start adding other data layers that might help explain the trends that we’re seeing,” said Shea Lemar, geographic information system senior project manager at ASU’s School of Geographical Sciences and Urban Planning.

“Being able to compare these response rates over time will really help us make a plan and be more successful in completing the next census,” Phillips said.

Beyond the direct impact it has on Congressional representation and federal funding allocation, improving the accuracy of census counts influences planning and decision making in every sector.

In January, the Knowledge Exchange for Resilience hosted the 2020 Census Matters Symposium, gathering leaders from across the state and the country to discuss the local impact of the decennial census. Journalism professionals spoke to the data’s importance as a demographic baseline for fact-checking, while nonprofit leaders noted how it could be used to supplement grant proposals to address community needs.

In the Arizona Office of Economic Opportunity, census counts are used to inform population estimates and projections.

“The base is the decennial census, so without the decennial census, there’s nothing we can do,” said Jim Chang, Arizona state demographer.

Researchers and academics, too, rely heavily on census data. “Having access to more accurate census data means that we as scientists are able to improve our understanding of the kinds of needs, shocks and stresses our communities are experiencing,” Solis said.

“Professionals of all fields utilize census data all the time to make the world better for their citizens,” Lemar said. “It is one of the most important data sources in the United States.”

To explore the 2020 Census Response Rates for Arizona map, visit