PPIC Logo Independent, objective, nonpartisan research
Blog Post · December 6, 2018

2020 Census: Counting California’s Northern and Sierra Regions

The decennial census plays an essential role in American democracy. Our series of blog posts examines what’s at stake for California and the challenges facing the 2020 Census, including communities that are at risk of being undercounted.  

PPIC’s interactive census maps are an important tool for Californians working to ensure an accurate census count. Using estimates from the Census Bureau and the Federal Communications Commission, they highlight hard-to-count communities across the state and pinpoint reasons why certain areas may be hard to reach.

Home to 1.4 million people, California’s northern and Sierra regions cover around 40% of the state, spanning 23 counties: Alpine, Amador, Butte, Calaveras, Colusa, Del Norte, Glenn, Humboldt, Inyo, Kings, Lake, Lassen, Mariposa, Mendocino, Modoc, Mono, Plumas, Shasta, Sierra, Siskiyou, Tehama, Trinity, and Tuolumne. The hardest-to-count areas in these regions are found in Arcata, Chico, and Mammoth Lakes in Humboldt, Butte, and Mono Counties, respectively. Households in these very hard-to-count areas are the least likely to respond initially to census forms, according to Census Bureau estimates that draw on local demographic characteristics (e.g., race/ethnicity, age, citizenship, and housing conditions) and historical trends.

Some highlights:

  • Follow-up from census workers will likely be needed across the north and Sierras. In most census tracts in California’s northernmost and rural Sierra counties, estimates suggest 19% to 29% of households would need in-person follow-up from census workers to be counted. Further, these estimates from the Census Bureau predate the Camp, Carr, and Mendocino Complex fires, which have likely made it more difficult to count residents.
  • Housing conditions could be an obstacle to counting residents in coastal areas as well as around the northern Sacramento Valley. In these areas, large shares of housing units are rentals, overcrowded rentals, and/or mobile homes—all of which can make residents harder to count accurately. For example, more than 20% of households live in mobile homes in much of Trinity and Tehama Counties, and one out of five rentals in northeastern Siskiyou County is overcrowd Recent wildfires have likely increased the share of households in hard-to-count housing, as displaced families seek shelter elsewhere.
  • Low internet access may pose a challenge throughout the regions. The Census Bureau plans to collect the majority of responses online in 2020—a change from previous practice. Northeastern and central Sierra counties have some of the lowest rates of internet access in the state: in Plumas County, for instance, fewer than 200 out of every 1,000 households have high-speed internet access, on average. In places with limited residential internet access, participation may rely more heavily on paper forms, in-person census takers, or internet provided by local institutions.
  • Undercounting Native Americans would disproportionately affect northern and Sierra counties. African Americans, Latinos, and Native Americans have historically been undercounted in the census. There are tribal lands throughout these regions, which have a higher share of Native American residents than other parts of the state. Working with tribal governments to reach Native Americans will be an important part of accurately counting residents in the northern and Sierra regions.
  • Local knowledge is necessary for effective outreach. Colusa County has the regions’ highest share of residents from historically undercounted racial/ethnic groups (60%) and the highest share of noncitizens (15%). Noncitizens may be less likely to respond to the 2020 Census due to the planned addition of a citizenship question and concerns about deportation and privacy. Ensuring that these communities are counted in 2020 will require an understanding of the local landscape. For example, one area east of Susanville in Lassen County that includes two correctional facilities has a high share of people of color. However, incarcerated people, who are counted where they are held, are unlikely to be undercounted in the census.
  • Some northern counties have high shares of young children. Young children are historically underrepresented in the census. Along the I-5 corridor in the Sacramento Valley, and in parts of Lake, Mendocino, Humboldt, Del Norte, Siskiyou, and Lassen Counties, more than 8.5% of residents are children under five years old, compared to 6.5% statewide.

We hope these maps serve as a starting point to help local, regional, and state leaders think about which activities, resources, and partnerships—including language assistance, awareness raising, and community outreach—might be most effective for accurately counting different parts of California. Stay tuned for future posts that examine hard-to-count communities in other regions of the state.


Census census undercount citizenship decennial census Health & Safety Net Political Landscape Population wildfires