STANDARD DEVIATIONS: Which Census Bureau Are We Talking About?

By Dr. William P. O’Hare

Standard Deviations blog posts represent the views of the author/organization, but not necessarily those of the Census Project.

I have been working with the Census Bureau and Census Bureau data since I started my PhD studies more than 50 years ago. I have written a couple of books on Census data accuracy along with numerous articles and reports on the Census. I have been on Census Bureau advisory committees and I have been a consultant to the Census Bureau.

Given that background, I was shocked by a recent suggestion that the Census Bureau and its long-standing imputation[1] program produce some sort of biased results, based on differences between the 2020 population estimates, and the actual census count.

There are several specific shortcomings in this line of thinking.

This perspective assumes the population estimates are more accurate than the census and should be used to determine how many members of congress each state deserves.

This is backwards. The Census Bureau’s population estimation program has been producing state population estimates every year for more than four decades. It is a partnership between states and the Census Bureau under the Federal-State Cooperative Program for Estimates (FSCPE). The estimates produced in this series are typically not thought of as being as accurate as the Census count. Every decade the Census Bureau, and demographers outside the Census Bureau – like those producing business demographics – use the decennial census count to assess the accuracy of their estimates and recalibrate their methodology based on the census count.  It is not unusual for the estimates to differ from the Census count… that is one reason we take a census every ten years.  No one should be surprised that the census counts and the population estimates do not match in the 2020 Census. This is not new…it happens every census. We take a census to recalibrate the population estimates series. If the estimates were as accurate as the census, the country could save billions of dollars by not conducting a census.

Some suggest a political motivation for the use of statistical imputation that sometimes produces a higher count in states they disfavor, while ignoring situations that are not consistent with their bias, inasmuch as imputation is used in blue and red states alike, adding more population than anticipated in some of each.[2]

A more reasonable explanation for why Census counts are higher than estimates in 2020 in some states has to do with the fact that the state governments in states (like California, New York and New Jersey) invested millions of dollars in outreach and state leaders did not join the Trump Administration’s effort to discourage immigrants from participating in the Census. That is consistent with the fact that census self-response rates in Hispanic-majority census tracts in Texas and Arizona are several percentage points below the national average while the self-response rates in California’s Hispanic-majority census tracts were several percentage points higher than the national average.[3]

Having worked with the Census Bureau staff for more than 50 years I feel very confident in saying it is the most non-partisan federal agency I know of. Any attempted politicization of the 2020 Census was due to the former administration which installed several unqualified political appointees at the last minute, tried to add a citizenship question to discourage immigrant participation in the Census, and tried to have undocumented immigrants removed from the apportionment count, among other things.  Census Bureau professional staff tried their best to resist the partisan pressures and conduct a typical non-partisan census. [4]

Similarly, those who seek to cast doubt about imputation, a widely used statistical technique among data producers, show their own bias. Studies show using imputation makes data more accurate than assuming occupied housing units are vacant which is the alternative when people don’t respond to a survey or the census. [5]

Whole-person imputations are used where there is evidence of a person existing but no information about that person. For example, in the Census some people are included by proxy respondent like a landlord or neighbor, who may say there are 4 people who live in a housing unit but can’t provide any more information. At that point, the Census Bureau has two choices, they can decide to leave those four people out of the Census count, or they can impute them. Studies show that imputing such individuals results in more accurate data. The Census Bureau uses information about the neighbors to impute data for the four-missing people. For example, if 90 percent of the neighbors are Asian, they are likely to impute the race of the four missing people as Asian. That makes sense.

The National Research Council,[6] determined that the 1.2 million imputations in the 2000 Census were problematic but concluded that if they had not been imputed the census “would have undoubtedly underestimated the true number of household resident…” According to Cohn, the U.S. Supreme Court concluded, “Without imputation, the court stated, the results would be ‘a far less accurate assessment of the population’” [7]

In the 2010 Census there were 1.2 million Hispanic people and 1.2 billion Black people imputed compared to 3.1 million Non-Hispanic Whites.[8] A higher number of Non-Hispanic White people were imputed than Black people and Hispanic people.

Another frequent complaint is that counting the undocumented is some sort of partisan maneuver. That claim requires disregarding the U.S. Constitution (Article I and Amendment XIV) which mandates that the Census Bureau count everyone living in the country including undocumented immigrants. That is what the Supreme Court ruled.  

I am also struck by facts that anyone claiming partisanship has to ignore in trying to build a case that the Census Bureau is adjusting the data in a partisan way to favor Democrats. The Decennial Census consistently overcounts the Non-Hispanic White population who are more right-leaning politically and undercounts minorities who are more left-leaning politically. In the 2010 Census, there were 6 million Non-Hispanic Whites double-counted while 1.7 million black people and 1.9 million Hispanic people were missed in the census. That is in my book… which perhaps new census critics should consult. [9]

It is not as if I have no complaints about the Census Bureau or concerns about the quality of the 2020 Census data (although the quality metrics I have seen so far, suggest the data from the 2020 Census is not likely to be as bad as some folks think).  But the kind of baseless attacks and misrepresentations of the Census and the Census Bureau reflected in partisan attacks needlessly erodes public trust in one of our basic institutions. The Census not only provides the basic data for reapportionment and redistricting, but it also provides key information that allows government programs to provide assistance to communities in an efficient and effective way. And for businesses to make decisions that lead to a more efficient economy. These recent attacks undermine support for public policy decisions based on data, evidence, and science   Maybe that is the point!

  • Dr. O’Hare, a member of The Census Project Advisory Committee, is a social demographer who has spent forty years using data to increase public understanding of disadvantaged groups. For the past 25 years, he has been involved in the KIDS COUNT project at the Annie E. Casey Foundation. Bill has a Bachelor of Science, Master of Arts, and a Ph.D. from Michigan State University.

[1]  Imputation is a statistical technic for estimating people and characteristics that are not reported by respondents.   For example, if a respondent does not provide their race when they are responding to the census and 90 percent of the block where they live are Asians, the Census Burau is likely to impute Asian for that respondents’ race.  This makes the dataset more accurate than leaving that item blank.

[2] U.S. Census Bureau (2021). A Preliminary Analysis of U.S. and State-Level Results from the 2020 Census, WP-104, U.S. Census Bureau, Washington DC.

[3] O’Hare, W. P. (2021). Measuring the Quality of the 2020 Census: What Do We Know Now? Presentation at the 2021 Population Association of American Conference, May 5,

[4] O’Hare, W.P. (2020). “The Politicization of the 2020 Census,” PAA Affairs, Fall 2020, The Population Association of America, Washington DC.

Frey, W. H.  (2020).  “Trumps new plan to hijack the census will imperil America’s Future,” Brooking Institute, August 7,

The Washington Post (2021. “Commerce department security Unit Evolved into counterintelligence-like operation, Washington Post examination found,” Shawn Boburg, May 24

[6] National Research Council (2004) The 2000 Census Counting Under Adversity.

[7] Cohn, D. (2011). Imputation: Adding People to the Census, Pew Research Center, Washington DC. MAY 4, 2011

[8] U.S. Census Bureau (2012). DSSD 2010 Census Coverages Measurement Memorandum Series #2010-E-51, Table C, U.S. Census Bureau, Washington, DC.  

[9] O’Hare W. P. (2019) Differential Undercounts in the U.S. Census: Who is Missing? Springer publishers, available open access at

Organizations Support the Census Deadline Extensions Act – S. 1267

The Census Project and the Leadership Conference on Civil and Human Rights led a letter from 106 organizations urging the Senate to “underscore the importance and urgency of extending statutory reporting deadlines for apportionment and redistricting data from the 2020 Census” and calling on Senators to “cosponsor the bipartisan 2020 Census Deadline Extensions Act (S. 1267), which would extend the statutory deadlines for delivering apportionment and redistricting data to May 1, 2021 and October 1, 2021, respectively, to reflect the updated 2020 Census timeline compelled by major pandemic-related delays and to establish certainty for states and localities that must draw new, fair electoral districts.”

The codification of these “new deadlines” would “restore predictability and certainty” in the drawing of electoral districts “for the next decade” and provide “certainty for the Census Bureau and the federal courts.”

To read the letter, click here.

Updates on the 2020 Census Quality Indicators – May 27

On May 27, the American Statistical Association posted its biweekly update regarding the status of the 2020 Census Quality Indicators efforts. The update is posted at:, the content for which is pasted below. The next update will be June 10.


May 27, 2021: The researchers are working closely with the Census Bureau to develop a set of 2020 Census quality indicators that provide a more complete picture for states. The data necessary for their work is being made available with increasing frequency and volume. To ensure sufficient time for a value-added understanding of the 2020 Census, the timetable will likely need to be adjusted, which members of the task force will clarify in the next update.

Senate Hearing on Commerce Department FY 2022 Budget Next Week

The Senate Commerce, Justice, Science (CJS) Appropriations Subcommittee will hold a hearing at 2pm on May 26, 2021 to discuss Fiscal Year 2022 funding for the Department of Commerce, which includes the Census Bureau. The hearing will come one day before the Biden Administration is expected to finally released their full FY 2022 budget proposal.

Commerce Secretary Gina Raimondo will testify.

Last month, The Census Project sent a letter signed by over 50 national, state, and local organizations urging the House and Senate CJS Appropriations Subcommittees to provide the Census Bureau with $2 billion in FY 2022, in line with The Census Project’s budget recommendation from March.

STANDARD DEVIATIONS: The First Assessment of 2020 Census Accuracy

By William P. O’Hare

Standard Deviations blog posts represent the views of the author/organization, but not necessarily those of the Census Project.

The Census Bureau’s release of the 2020 Census apportionment counts on April 26, 2020, provides the first opportunity to compare the Census counts to the estimates from Demographic Analysis. Demographic Analysis (DA) estimates are prepared by Census Bureau staff to provide an estimate of the population they expect to find in the Census, and they have been used to assess Census accuracy for more than half a century. The DA estimates are based largely on data from birth and death certificates along with Medicare data and data on immigration from abroad. The DA estimates are widely believed to be very accurate for data at the national level.

The Middle Series of the DA estimates for the total population released on December 15, 2020, was 332,601,000 (U.S. Census Bureau 2020) and the Census count of the resident population in the 2020 Census was 331,449,281 (U.S. Census Bureau 2021).   Thus, the Census count was 1,151,719 below the Middle Series DA estimate which results in a net undercount rate of 0.3 percent.  

Keep in mind this is a NET undercount figure. It does NOT reflect the number or rate of people missed in the Census. The NET undercount is basically a balance between those missed and those counted more than once (O’Hare et al. 2020). Data on omissions and erroneous enumerations in the 2020 Census won’t be available until data from the Census Bureau’s Post-Enumeration Survey are released (probably in 2022).

Figure 1 provides the 2020 Census coverage estimate along with similar Demographic Analysis assessments from 1950 to 2010.

While the net undercount of 0.3 percent in the 2020 Census, is a slight increase from the 2010 Census coverage rate, the net undercount of 0.3 percent is not very different from the coverage rates in the 2000 or 2010, and 2020 Census coverage looks much better than the coverage rates of censuses of from 1950 to 1990. By this measure, it appears the 2020 Census is not quite as good as the 2000 and 2010 Census, but it is not the train wreck some folks predicted. However, more analysis is needed to provide a solid assessment of the 2020 Census quality.

Despite this relatively good news about the overall accuracy of the 2020 Census, it is important to remember what is really important about Census accuracy is differential accuracy: that is the relative accuracy of census counts among subgroups and across places. The overall accuracy for the total population at the national level can mask important differences among groups. As shown in Figure 1, the overall coverage rate in the 2010 Census was quite good, but that masks the fact that the net undercount rate for the black population was 2.5 percent and it was 1.5 percent for Hispanics (O’Hare 2019). For young children (ages 0 to 4) the net undercount rate in the 2010 Census was 4.6 percent and for Black and Hispanic young children, the net undercount rates were in the neighborhood of 6 or 7 percent (O’Hare 2015).

The analysis presented here suggests that the 2020 Census coverage was relatively good in terms of the overall national population, but the real assessment of census accuracy will be seen when data become available to assess the coverage of subgroups. 


Updates on the 2020 Census Quality Indicators

On May 13, the American Statistical Association posted its biweekly update regarding the status of the 2020 Census Quality Indicators efforts. The update is posted at:, the content for which is pasted below. The next update will be May 27.


In October 2020, the American Statistical Association released the 2020 Census Quality Indicators, a report written by a task force of census experts with a plan to shed light on the quality, accuracy, and coverage of the 2020 Census counts. The report proposed various measures of quality, accuracy, and coverage spanning the multiple decennial census components to be applied to the 2020 data as it became available.

Sign up to receive 2020 Census Quality Indicator updates

Updates on the quality indicator developments will be posted to this page:

  • May 13, 2021: The researchers are working closely with the Census Bureau on the development of a series of tabulations, from which key indicators will be drawn. This involves assessing the conceptual basis of the quality indicators, checking to ensure those indicators have sound empirical support, and constructing and verifying the categories of the tables from which the indicators are derived. A recent push by the Census Bureau to provide more resources for the researchers makes them optimistic they can release a first report in June.
  • April 29, 2021
  • April 15, 2021: The researchers have been provided the first set of their requested quality-indicator data and are examining it to understand its implications. They remain in regular contact with US Census Bureau staff. With the White House news this week that President Biden intends to nominate Robert Santos to be director of the US Census Bureau, Santos resigned from the task force, effective immediately. Ken Prewitt also resigned from the task force following his appointment to be a senior adviser in the office of the census director. The task force has no other updates.
  • April 1, 2021: The researchers are in the early stages of working with the US Census Bureau statistical programmers on the 2020 Census data. They continue to be in regular contact with the bureau disclosure avoidance staff. The likely timing for the first report is still sometime in June. The ASA task force otherwise has no updates.
  • March 18, 2021
  • March 4, 2021: Since the February 18 update, the three researchers have continued their work, refining their planned analyses, applying them to the 2010 data, and reflecting on data quality measurement observations from the February JASON report. This work is being carried out with key Census Bureau staff, particularly to better identify and interpret the most important indicators.
    So the researchers can carry out their work objectively and unhindered, please do not contact them directly.
  • February 18, 2021
  • February 4, 2021

New CRS Report on the Apportionment and Redistricting Process

“Whereas apportionment is a process largely governed by federal statute,” according to a new repot from the Congressional Research Service (CRS), “redistricting is a process, in practice, largely governed by state law.” Some federal-level requirements focused on “preserving equal access to representation” apply to the drawing of House districts, “but the method and timeline by which those districts are created is largely determined by state law. In states with multiple congressional districts, there are a multitude of ways in which district boundaries can be drawn, depending upon the criteria used to create the districts. There is often an expectation that congressional districts will be drawn in a way that ensures “fair” representation, but “fairness” can be a somewhat subjective determination.”

Redistricting criteria currently “reflect a combination of state and federal statutes, judicial interpretations, and practices from past redistricting cycles that may require trade-offs between one consideration and another.” While “equal population size across all congressional districts, for example, may be an agreeable goal for many individuals… the geographic and demographic distribution of residents within and across states, coupled with requirements to observe state boundaries, provide all states with at least one Representative, and maintain a constant number of House seats, make this goal more difficult to achieve.” Despite the rise of hyper-precise mapmaking software, “this technological capacity has not necessarily simplified the overall task of redistricting.”

CRS warned that litigation over congressional redistricting has become normal: “A majority of states faced legal challenges to congressional district maps drawn following the 2010 census, reflecting differing perspectives on fairness, representational access, and how competing redistricting criteria should be weighted.”

Next Census Scientific Advisory Committee Meeting is May 25, 2021

The Census Scientific Advisory Committee will next meet (virtually) on May 25, 2021 (11:00 a.m. to 2:30 p.m. Eastern), to “address ongoing outreach efforts needed to assist with the designing of a differential privacy suite for the 2020 Census data products that will meet programmatic, legal, and statistical requirements, including work on both the primary and secondary disclosure avoidance systems.”

This committee “provides scientific and technical expertise to address Census Bureau program needs and objectives” and its members are appointed by the Census Bureau Director.

While the meeting sets aside time for public comments, any extensive questions or statements are requested to be sent to, (subject: “CSAC Differential Privacy Virtual Meeting Public Comment”).

The meeting will be held via WebEx:​uscensus/​onstage/​g.php?​MTID=​e351f8ffcb2e21b2437a649a206a6d8d3

Census Bureau Releases 2020 Census Apportionment Data

On April 26, the U.S. Census Bureau announced the first major results from the 2020 Census— state population counts used to apportion seats in the U.S. House of Representatives. The results included the following:

  • The resident U.S. population (as of April 1, 2020) is 331,449,281 million.
  • This number represents a 7.4% increase over the 2010 Census population total.
  • While the nation’s population has increased since the last decennial census, the growth rate was lower than the increase that the nation experienced between the 2000 and 2010 Census. In fact, the rate of growth between 2010 and 2020 is the second lowest rate of growth that the nation has experienced since the census began in 1790.
  • In terms of the number of congressional seats each state gained or lost, Texas gained the most (2 seats), while 5 states gained one seat (Colorado, Florida, Montana, North Carolina, and Oregon). Seven states (California, Illinois, Michigan, New York, Ohio, Pennsylvania, and West Virginia) lost a congressional seat.

It should be noted that the U.S. resident population represents the total number of people living in the 50 states and the District of Columbia. The apportionment count includes military and civilian personnel stationed overseas and their families.

The Census Bureau will be releasing the full redistricting data file, which provides more granular information about the population at the block level, before the end of September 2021.

What to Make of the 2020 Apportionment Counts?

We recently recommended a new online tool from the Census Bureau to help stakeholders work with 2020 Census apportionment data once it is released this month.

The “Historical Apportionment Data Map” displays apportionment results for each census. While it currently just includes 1910 to 2010, the Bureau has said that the 2020 apportionment data will be added to the map as soon as they become public.

It is important to be reminded that the state apportionment counts differ significantly from the final 2020 state population totals that will come later, as well as the annual Population Estimates for each state. The apportionment calculation is based upon the total resident population (citizens and noncitizens) of the 50 states. In 2020 the apportionment population also includes U.S. Armed Forces personnel and federal civilian employees stationed outside the United States and their dependents living with them that can be allocated back to a home state. The population of the District of Columbia is not included. More can be found here.

The most recent population estimates are a rough tool used by experts to project the apportionment such as here and also here. While generally close to the official apportionment release, readers are cautioned that small differences can affect which state gets the 435th seat in the House of Representatives.

Quality of the Counts

For the first time ever, the Census Bureau will also release some process indicators that will be our first hint of how well the 2020 count went. These indicators will not tell us about important metrics on the overall quality or completeness of the count, (such as the net undercount or the differential undercount across race subgroups), but they will begin to tell the story of how well the Bureau adapted to disruptions in operations cause by the Covid-19 pandemic. Look for the Bureau to report on state level indicators such as:

  • The percent addresses determined to be occupied, vacant, or non-existent.
  • How Census determined household status. That is through self-response, in person interview, Group Quarters or unresolved.
  • For other than self-response, the  percentage of occupied addresses resolved by interview, proxy, or administrative records.
  • The percent of deleted addresses later resolved with a proxy interview or by administrative records.

On Wednesday, April 21, 2021 at 1 p.m. EDT, the Census Bureau will host an Educational Webinar on these metrics.  Where possible the Bureau will compare to 2010 metrics of the same kind. Beginning in May, the Bureau will begin progressively releasing other quality metrics, including an independent analysis by a outside team led by experts from the American Statistical Association.