Annual estimates of U.S. population with demographic detail, components of change (births, deaths, migration); at the national, regional and state levels, from 1900; at the metro area and county levels, from 1970.
The Census Bureau develops population estimates with a component of population change method in which they use administrative records to estimate the household and group quarters population. For the household population, the components of population change are births, deaths, net domestic migration, net international migration, and net overseas military movement. They measure change in the non-household, or group quarters, population by the net change in the population living in group quarters facilities.
A major assumption underlying this approach is that changes in selected administrative or survey data sources closely approximate the components of population change. Therefore, Census Bureau demographers separately estimate each component of population change based on administrative records, including registered births and deaths, Federal income tax returns, Medicare enrollees, and military movement. They also incorporate data from the American Community Survey into the estimates.
The Census Bureau produces the estimate of each area’s population, starting with the base population from either Census 2000 (for the July 1, 2000 estimates) or the revised population estimate for the most recent year (for the July 1 estimates of all years after 2000). They then add or subtract the demographic components of population change calculated for that time period. Basically, this measns they add the estimated number of births and subtract the estimated number of deaths for the time period. Next, they add (or subtract, as appropriate) the estimates of net domestic migration, net foreign-born international migration, net movement to/from Puerto Rico, net overseas Armed Forces movement, net native migration to/from the United States, and the change in group quarters population.
Births - total number of live births occurring to residents of an area during a time period, as estimated using reports from the Census Bureau’s Federal-State Cooperative Program for Population Estimates (FSCPE) and the National Center for Health Statistics. The birth rate expresses births during a time period as a percentage of an area’s population at the midpoint of the time period.
Deaths - total number of deaths occurring to residents of an area during a time period, as estimated using reports from the Census Bureau’s Federal-State Cooperative Program for Population Estimates (FSCPE) and the National Center for Health Statistics. The death rate expresses deaths during a time period as a percentage of an area’s population at the midpoint of the time period.
Net Internal Migration - the difference between internal in-migration to an area and internal out-migration from the same area during a time period. Internal in- and out-migration consist of moves where both the origin and the destination are with in the United States (excluding Puerto Rico). The net internal migration rate expresses net internal migration during a time period as a percentage of an area’s population at the midpoint of the time period.
Net International Migration - International migration, in its simplest form, is defined as any movement across U.S. (50 states and District of Columbia) borders. The U.S. Census Bureau makes estimates of net international migration for the nation, states, and counties. We estimate net international migration as: (1) net migration of the foreign born, (2) net movement from Puerto Rico, (3) net movement of the U.S. Armed Forces, and (4) emigration of the native born. The largest component, net migration of the foreign born, includes lawful permanent residents (immigrants), temporary migrants (such as students), humanitarian migrants (such as refugees), and people illegally present in the United States. Currently, they do not estimate these components individually
Data is revised annually. With each annual release of population estimates, the Population Estimates program revises and updates the entire time series of estimates from April 1, 2010 to July 1 of the current year. The release of a new estimates supersedes any previous series and incorporates the most up-to-date input data and methodological improvements.