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The Census Is Finished but Questions About Data Quality Linger

By Christi Zamarripa  |  September 15, 2022

State legislators and the U.S. Census Bureau have more in common than you might think. Legislators get to know their constituents by meeting them in their homes, neighborhoods and communities. Likewise, the bureau meets with the public when canvassing and conducting survey meetings. Legislators consider new ideas to decide whether new laws are needed. The bureau uses public feedback to improve the agency’s processes.

“I need to understand the diverse needs of communities—from urban to suburban neighborhoods as well as rural counties, ranches, tribal lands—and of course, the needs of the state and local governments,” Robert L. Santos, director of the Census Bureau, told a session at the NCSL Legislative Summit.

As a trusted data steward, the bureau conducts not only the decennial census but also more than 130 surveys annually. That data helps legislators (and virtually everyone in the U.S.) make informed, evidence-based decisions in many important policy areas.

Like legislators, bureau workers sometimes need to alter their approach to adapt to new challenges and constituent input. When the operational plan for the 2020 decennial census was put together, no one foresaw the global pandemic or the ways it would disrupt the bureau’s enumeration efforts. And decisions separate from the pandemic, including a new method for protecting privacy, generated concerns about data quality.

Although the bureau managed to complete the census during a pandemic, questions about data quality remain:

  • Is the decennial census fit for use? Yes: “Our 2020 decennial census data are fit for the purposes of congressional apportionment and legislative redistricting,” Santos said.
  • Is the 2020 baseline data accurate? Maybe: “When looking at vital statistics—health, births, deaths—the importance of having accurate baseline data is critical,” Colorado state demographer Elizabeth Garner said. Further evaluation is needed.
  • Has differential privacy created impossible and improbable outcomes? Differential privacy is the bureau’s new method of preserving the confidentiality of information from individuals and households by adding “noise” to the data. And the answer is yes: “Hands down, it is less accurate data now at smaller, lower levels of geography” for which the data is not as good as it is for larger counties and larger cities, Garner said.
  • Is new data forthcoming? Yes: The stateside Demographic and Housing Characteristics file is expected in May 2023, according to James Whitehorne, chief of the U.S. Census Bureau. “Also, in early 2023, the bureau will take the new congressional and legislative districts, retabulate the ACS and create new demographic profiles,” he said, referring to the American Community Survey.

The census is a once-a-decade event, but preparation is continuous. So where do the bureau and stakeholders, including states, go from here?

  • The bureau is collecting feedback from stakeholders about its research and findings to clarify needs and data gaps. Research has already begun in five areas that affect the quality and cost of the census: data collection, data processing, counting people in group quarters, infrastructure operations and coverage equality.
  • State, local and tribal governments that identify data anomalies can seek appeals through the 2020 Census Count Question Resolution Operation and the 2020 Post-Census Group Quarters Review. Any reviews will be used for future data releases but will not alter redistricting data.
  • States can make permanent the programs they used to encourage a complete count in the run-up to the 2020 census. “‘Evergreen’ your census programs by recognizing that census counts do not end and your role in working with the Census Bureau must be continuous,” said James Tucker, senior special counsel at the Lawyers’ Committee for Civil Rights Under Law. “This may be the great unknown civil rights issue and the great unknown budgetary issue in the states that people don’t realize: That as much information as you get from the decennial census, you get even more information from the American Community Survey that affects people’s daily lives.”

Census perfection is impossible, and the data is always subject to some level of uncertainty and systemic error. But it’s the data of record for congressional reapportionment and for redistricting, and it provides valuable insight in the areas of health, education, housing, employment and beyond. Santos put it best: “The bottom line is that census data in all of its forms and all of its sources helps our nation to function, it helps us to grow, it helps us to prosper and, yes, it helps preserve and advance our democracy.”

Christi Zamarripa is a policy associate in NCSL’s Elections and Redistricting Program.

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