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National Terms and Definitions

Base Population - The population count or estimate used as the starting point in the estimates process. It can be the last Census count or the estimate for a previous date.

Births - Total number of live births occurring to residents of the United States as estimated by the Census Bureau using data from the National Center for Health Statistics.

Civilian Noninstitutionalized Population - The civilian population excluding persons residing in institutions. Such institutions consist primarily of nursing homes, prisons, jails, mental hospitals, and juvenile correctional facilities.

Civilian Population - The portion of the resident population not in the active-duty military.

Components of Population Change - The demographic components of population change are births, deaths, and net migration.

Deaths - Total number of deaths occurring to residents of the United States as estimated by the Census Bureau using data from the National Center for Health Statistics.

Mean Age - The average age of all the members of a population.

Median Age - The age which divides the population into two numerically equal groups; that is, half the people are younger than this age and half are older.

Natural Increase - The difference between the number of births and the number of deaths.

Net Armed Forces Movement - The net movement of Armed Forces personnel in and out of the United States (excluding Puerto Rico).

Net International Migration - Any change of residence across the borders of the United States (50 states and District of Columbia). The U.S. Census Bureau makes estimates of net international migration for the nation, states, and counties. We estimate net international migration in four parts: (1) net international migration of the foreign born, (2) net migration between the United States and Puerto Rico, (3) net migration of natives to and from the United States, and (4) net movement of the Armed Forces population between the United States and overseas. The largest component, net international 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, we do not estimate these components individually. The Census definition of foreign born is available on the foreign-born population page.

Resident Population - The resident population includes all residents (both civilian and Armed Forces) living in the United States. The geographic universe for the resident population is the 50 states and the District of Columbia.

Resident Population plus Armed Forces Overseas - The residents of the United States and members of the Armed Forces on active duty stationed outside the United States. Military dependents and other United States citizens living abroad are not included.

Residual - Results from two parts of the estimates process:

  1. the application of national population controls to state and county population estimates and
  2. the incorporation of accepted challenges and special censuses into the population estimates. The residual represents change in the population that cannot be attributed to any specific demographic component of population change.

Source: U.S. Census Bureau | Population Estimates |  Last Revised: May 23, 2013