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 proportion of an area's population at the midpoint of the time period. Rates are expressed per 1,000 population.

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 proportion of an area's population at the midpoint of the time period. Rates are expressed per 1,000 population.

Occurrences used by the Census Bureau to estimate changes in the population during a time period. These components consist of births, deaths, net domestic migration and net international migration.

Federal Information Processing Standards (FIPS) codes issued by the National Institute of Standards and Technology (NIST) that identify each geographic area.

Births minus deaths. The rate of natural increase expresses natural increase during a time period as a proportion of an area's population at the midpoint of the time period. Rates are expressed per 1,000 population.

The difference between domestic in-migration to an area and domestic out-migration from the same area during a time period. Domestic in- and out-migration consist of moves where both the origin and the destination are within the United States (excluding Puerto Rico). The net domestic migration rate expresses net domestic migration during a time period as a proportion of an area's population at the midpoint of the time period. Rates are expressed per 1,000 population.

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
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. The international migration rate expresses net international migration during a time period as a proportion of an area's population at the midpoint of the time period. Rates are expressed per 1,000 population.

Net domestic migration plus net international migration. The net migration rate expresses net migration during a time period as a proportion of an area's population at the midpoint of the time period. Rates are expressed per 1,000 population.

The difference between the population of an area at the beginning and end of a time period.

The difference between the population of an area at the beginning and end of a time period, expressed as a percentage of the beginning population.

The calculated number of people living in an area as of July 1. The estimated population is calculated from a component of change model that incorporates information on natural change (births, deaths) and net migration (net domestic migration, net international migration) that has occurred in an area since the latest decennial census.

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.