The mission of the decennial census is to count everyone living in the United States once, only once, and in the right place. Accurate counts are important because census results are used to allocate seats in the House of Representatives, to redistrict, and to distribute around $400 billion in federal funds each year. Fulfilling this mission is daunting in a country that is growing increasingly more diverse and complex.

Despite best efforts to count everyone, the U.S. Census Bureau’s own record of research shows persistent differential undercounts of some minority populations across decennial censuses, such as among African Americans and Hispanics. Prior ethnographic studies conducted during census data collection operations, but separate from those operations, have identified a range of factors affecting coverage and illuminated how and why they may affect enumeration in some populations. However, previous ethnographic studies have not included systematic observations of live interviews and respondents in an actual decennial census environment.

The present evaluation was conducted to address this gap, in addition to addressing the overall need to increase the understanding of the types and sources of these persistent miscounts in the census. In this report, the authors present findings from comparative ethnographic and partial validation research. The goal of this evaluation was to explore types and sources of possible census coverage error and identify the characteristics of households and of persons affected by them through observation of live, in-person 2010 Census interviews. We aimed to identify similarities and differences across race/ethnic groups to contribute to the discussion of why differential counts persist and to suggest improvements and new research for the next census.