Population Estimates

Methodology: Resident Population Estimates of the United States

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Resident Population Universe Definition

Estimates of the United States resident population include persons residing in the 50 States and the District of Columbia. They exclude residents of the Commonwealth of Puerto Rico, and residents of the outlying areas under United States sovereignty or jurisdiction (principally American Samoa, Guam, Virgin Islands of the United States, and the Commonwealth of the Northern Mariana Islands). The definition of residence conforms to the criterion used in Census 2000, which defines a resident of a specified area as a person "usually resident" in that area. Estimates of resident population exclude the United States Armed Forces overseas, as well as civilian United States citizens whose usual place of residence is outside the United States.

Postcensal Estimation of Resident Population

Estimates of the United States population were derived quarterly by updating the resident population enumerated in Census 2000 through the components of population change. The following formula was applied to update the population:

1. 2000 enumeration of resident population,
2. + births to U.S. resident women,
3. - deaths to U.S. residents,
4. + net international migration,
5. + net movement of U.S. Armed Forces.
1. The 2000 enumerated resident population comes from the April 1, 2000 Decennial Census. For vintage 2005, the estimates base reflects corrections to the Census 2000 population from Count Question Resolution and Notes and Errata.
   

2. Registered births to United States resident women are estimated from data supplied by the National Center for Health Statistics. The primary source for this birth data can be found in National Center for Health Statistics (NCHS), National Vital Statistics Reports, Volume 54, Number 2, “Births: Final Data for 2003,” and similar publications of NCHS.

3. Registered deaths to United States residents are also estimated from data supplied by the National Center for Health Statistics. The primary source for this death data can be found in the National Center for Health Statistics, National Vital Statistics Report, Volume 53, Number 5, "Deaths: Final Data for 2002," and similar NCHS publications.

4. International migration, in its simplest form, is defined as any movement across United States (50 states and District of Columbia) borders. The U.S. Census Bureau makes estimates of net international migration for the nation, states, and counties. The net international migration component combines three parts: (1) net migration of the foreign-born, (2) emigration of natives, and (3) net movement between Puerto Rico and the United States. In an effort to maximize the use of available data, we used 2000-2004 American Community Survey (ACS) data as the basis for the level of net migration of the foreign born. After determining the annual net change in the size of the foreign-born population, we accounted for deaths to the entire foreign-born population during the periods of interest to arrive at the final estimate of net migration of the foreign born. In order to account for variability due to small sample sizes of the foreign born, we used a moving average for the period changes to get the final net foreign-born migration estimate. We applied the age-sex-race-Hispanic origin-county distribution of the non-citizen foreign born from Census 2000 who entered in 1995 or later to the national-level estimate of net migration of the foreign born.
   
   The two remaining parts of the net international migration component, the net movement between Puerto Rico and the United States and the emigration of natives, were produced in similar ways. For both parts, we do not have current, annually-updated information. Therefore, we used the previous vintage’s levels of movement.¹ For both parts, we applied the age-sex-race-Hispanic origin-county distributions from Census 2000 that were most similar to the population of interest. For the net movement between Puerto Rico and the United States, the distribution was based on the characteristics (age, sex, race, Hispanic origin, and county of residence) of the Census 2000 population who were born in Puerto Rico and who had entered the United States in 1995 or later. For native emigration, we assumed these emigrants were likely to have the same characteristics distributions as natives who currently reside in the United States. Therefore, the age-sex-race-Hispanic origin-county distribution of natives residing in the 50 states and the District of Columbia was applied to the native emigrant population.
   
   Once the net migration of the foreign born, net movement between Puerto Rico and the United States, and emigration of natives were estimated, the three parts were combined to estimate a final net international migration component. Net international migration is equal to net migration of the foreign born plus net migration between Puerto Rico and the United States minus net emigration of natives.

5. Armed Forces overseas strength statistics are supplied by the five branches of the Armed Forces in the Departments of Defense (Army, Navy, Marines, and Air Force) and Transportation (Coast Guard).

Population estimates are subject to revision, as revised input data become available. These revisions normally occur once a year.

¹For more information on the estimate of 11,133 for the net movement from Puerto Rico see Christenson, M. “Evaluating Components of International Migration: Migration Between Puerto Rico and the United States,” Population Division Technical Working Paper No. 64. For information on estimates of native emigration see Gibbs, J. G. Harper, M. Rubin, and H. Shin, “Evaluating Components of International Migration: Native-Born Emigrants,” Population Division Technical Working Paper No. 63.