What is the census?

The census is the official count of every person living in the United States, conducted every ten years by the U.S. Census Bureau, an agency within the Department of Commerce. The U.S. Constitution requires the census in Article I, Section 2, which directs that an actual enumeration of the population shall be made every ten years for the purpose of allocating seats in the House of Representatives. The first U.S. census was conducted in 1790 under the supervision of Thomas Jefferson, then Secretary of State. It counted just under 4 million people across the original 13 states and the territories that would become Vermont, Kentucky, Tennessee, Maine, and Ohio. The most recent census was conducted in 2020 and counted approximately 331 million people.

The census collects information from every household in the country, including the number of people living there, their ages, sex, race, ethnicity, and relationship to one another. The census does not ask about citizenship status, though such a question has been proposed and debated in recent years. Federal law requires that all census responses be confidential and used only for statistical purposes. Personal information collected in the census cannot be released to law enforcement, immigration authorities, or other government agencies, and Census Bureau employees swear an oath to protect the data.

The census has profound political and economic consequences. The results determine how the 435 House of Representatives seats are apportioned among the 50 states. After the 2020 census, Texas gained two seats, while California, Illinois, Michigan, New York, Ohio, Pennsylvania, and West Virginia each lost one. Census results also determine each state's number of electoral votes, since electoral votes equal the number of representatives plus two senators.

The federal government uses census data to allocate more than 1.5 trillion dollars per year in federal funds for programs including Medicaid, Medicare, the Supplemental Nutrition Assistance Program, federal highways, education programs, and many others. State and local governments, businesses, researchers, and journalists also use census data extensively.

The census faces ongoing challenges including ensuring an accurate count of all communities, particularly people who have historically been undercounted (such as immigrants, low-income communities, communities of color, young children, and people in rural areas). The Census Bureau also conducts the American Community Survey, a continuous survey of a smaller sample of households that provides more detailed demographic and economic information than the decennial census.