U.S. Data in DataFinder
The U.S. data used in PRB’s DataFinder database are from the U.S. Census Bureau’s decennial census, American Community Survey, and population estimates.
More detailed sources are available from PRB.
U.S. Decennial Census
The Decennial Census is primarily a mail-out/mail-back survey conducted every 10 years to enumerate the U.S. population and apportion the seats in the U.S. House of Representatives. Additional purposes include redrawing the boundaries of congressional and state legislative districts and ensuring accurate distribution of federal funds to a wide range of federal, state, local, and tribal governments. More than $400 billion in federal funds are allocated annually based on decennial census data.
Decennial census data reflect the population as of April 1 and are available for states, counties, cities, neighborhoods, and many other geographic areas. Data are available from the Census Bureau’s American FactFinder website at http://factfinder2.census.gov.
American Community Survey
The American Community Survey (ACS) is a nationwide, continuous survey designed to provide communities with reliable and timely demographic, housing, social, and economic data every year. Single-year ACS estimates are available for geographic areas with at least 65,000 people. The U.S. Census Bureau produces five-year ACS estimates for areas as small as census tracts.
All ACS estimates are subject to both sampling and nonsampling error, and PRB suppressed percentages in cases where the confidence interval exceeded 10 percentage points. Data are available from the U.S. Census Bureau’s American FactFinder website at http://factfinder2.census.gov.
U.S. Population Estimates
The U.S. Census Bureau’s Population Estimates Program produces estimates of the total resident population by age, gender, race, and Hispanic origin for the nation, states, and counties. It also publishes the demographic components of population change (births, deaths, and migration). The population estimates are based on the 2000 Decennial Census and updated each year based on annual information about births, deaths, and migration. Population estimates refer to the population as of July 1 of each year.
Vintage years reflect the most recent year for which estimates are updated. When estimates are updated, estimates from all the prior years since the last census are revised to account for new data. The new estimates thus supersede all previous estimates. Population estimates are available from the Census Bureau’s website at www.census.gov/popest/estimates.html.