The U.S. Constitution requires a population census every 10 years for apportioning seats in the House of Representatives. Decennial census data are used, too, for within-state redistricting and in certain formulas for distributing more than $450 billion annually in federal funds to states and localities. Census counts also are the foundation for estimates of current population size between censuses and projections of future size. Businesses, nonprofit organizations, researchers, and all levels of government are steady consumers of decennial and other census data. The bureau's task in conducting the enumeration can be summarized in very basic terms: count each person whose usual residence is in the United States (the aim of complete census coverage); and count that person only once, at the right location, where the person lives all or most of the time (the goal of census accuracy). This book highlights key issues pertaining to the 2020 Census.