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Major Census Quality Check Spotlights Persistent Undercounts

The results of the Census Bureau’s Post-Enumeration Survey reveal inequities that require concerted action to fix.

Last Updated: May 24, 2022
Published: March 15, 2022

Over the past few months, the Census Bureau has been publishing the results of its major qual­ity check on the 2020 Census. While the bureau’s initial findings from the Post-Enumer­a­tion Survey suggest that the census very accur­ately coun­ted the total number of people living in the coun­try, they also show that this decade’s data suffered from the same seri­ous prob­lem as past censuses: signi­fic­ant under­counts in many communit­ies of color. The bureau’s subsequent findings, moreover, reveal that not all states were counted equally well.

These data problems complic­ate the census’s abil­ity to perform its basic func­tions and should spur action for future fixes.

What is the Post-Enumeration Survey?

The Post-Enumer­a­tion Survey is a sample survey the bureau conducts shortly after the decen­nial census. Its goal is to meas­ure how well the Census Bureau coun­ted people and captured basic demo­graphic inform­a­tion, specific­ally the age, sex, race, and ethni­city of each person in the coun­try. This data is used to produce two estim­ates that help eval­u­ate the coun­t’s accur­acy. The first is how many people were under­coun­ted or over­coun­ted in the census, known as “net cover­age error.” The second is how many people were correctly coun­ted, erro­neously coun­ted, or missed alto­gether, known as “compon­ents of cover­age.” This data gives the public a sense of how accur­ate the 2020 Census ulti­mately was compared to prior censuses, and it gives the bureau a sense of what it needs to improve before the next one.

Why is it important to have an accurate census?

The stakes of the census are high. Decen­nial census data is used to divide seats in the House of Representatives and Elect­oral College votes among the states. It is also used to redraw district maps used for voting and to distrib­ute over $1 tril­lion in fund­ing every year for services like food, schools, and health­care. Getting the count right is essen­tial to ensur­ing that every­one receives their fair share of demo­cratic representation and govern­ment support.

The stakes of this decade’s census are espe­­cially high for communit­ies of color. The nation’s popu­la­­tion growth over the past 10 years came entirely from nonwhite communit­ies. For these communit­ies to receive polit­ical repres­ent­a­­tion and crit­ical invest­­ments commen­sur­ate with their size, they must be coun­­ted fully.

Inac­curacies in census data that fall along racial lines, in turn, perpetu­ate systemic discrim­in­a­tion against and disen­fran­chise­ment of communit­ies of color by depriving those groups of polit­ical power and public services.

What are the major takeaways from the Post-Enumeration Survey?

The pandemic and unpre­ced­en­ted meddling by the Trump admin­is­tra­tion led to worries about a disastrous 2020 count. The Post-Enumeration Survey results indic­ate that the national popu­la­tion count was unaf­fected by these chal­lenges — the 2020 Census did not have a stat­ist­ic­ally signi­fic­ant under­count rate over­all. However, that national stat­istic hides the more alarm­ing trend of racially inequit­able under­counts, an issue the census has consist­ently faced. The top-level results also mask disparities in the count’s accuracy among the states.

The Post-Enumer­a­tion Survey shows that in 2020, people who identify as Black, Hispanic/Latino, Native Amer­ican and Alaskan Natives living on reser­va­tions, or Some Other Race were signi­fic­antly under­coun­ted, while white non-Hispanic and Asian people were over­coun­ted, and Native Hawaiian and Pacific Islander people were neither over­coun­ted nor under­coun­ted. The Hispanic popu­la­tion, moreover, went under­coun­ted at over three times the rate it was in 2010.

Meanwhile, six states were undercounted at a statistically significant rate in 2020: Arkansas, Tennessee, Mississippi, Florida, Illinois, and Texas. Eight states, on the other hand, were overcounted: Ohio, Massachusetts, Utah, New York, Minnesota, Rhode Island, Delaware, and Hawaii.

The Census Bureau states that the overcounts and undercounts in the 2020 Census were not outside the range of expected variability based on prior decades. The 2010 PES suggested that no states had statistically significant undercounts or overcounts, while the 2000 PES estimated 22 states and D.C. had statistically significant problems of that kind. The Bureau cautions, however, that uncertainties associated with the methods it used in those earlier quality checks make it difficult to make historical comparisons of these quality statistics.

What should be done to improve future censuses?

Plan­ning for the 2030 Census is already under­way, and the results of the Post-Enumer­a­tion Survey show that the bureau needs to prior­it­ize redu­cing racial and ethnic differ­en­tial under­counts the next time around. The bureau should take a hard look at its current count­ing prac­tices and research how it can improve all levels of the census process to ensure fairer counts. Internet responses, for example, helped insulate the 2020 count from the COVID-19 pandemic’s disruptive effects, but the digital divide — that is, unequal access to broadband services across racial and ethnic groups — means that moving the census to the internet can’t ensure an accurate count. Congress should fully fund bureau efforts to study and improve its counting methodologies, as well as consider reforms that would safe­guard the bureau’s inde­pend­ence and enhance the accur­acy, inclus­iv­ity, and equity of the count. Lawmakers should also consider chan­ging the formu­las used to distrib­ut­e federal fund­ing to compensate state and local govern­ments for under­counts in their juris­dic­tions.

The difference in state-level accuracy also suggests that robust get-out-the-count efforts led by states, localities, and civil society groups may enhance the quality of the count. States that invested in census operations and get-out-the-count efforts — such as California with its $187 million investment — faired better than those that refused to invest in the census like Texas and Florida.

An equit­able census that counts all groups equally well would not only produce more accur­ate numbers, it would result in a distri­bu­tion of polit­ical power and fund­ing where every community gets its fair share. The 2020 Post-Enumer­a­tion Survey results under­score the need for the Census Bureau, Congress, and other stakeholders to work together to ensure that the next decen­nial census does better.