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Source: U.S. Bureau of the Census, Population Estimates Program (PEP). Updated annually.
http://www.census.gov/population/www/estimates/popest.html Estimates are made for the United States, areas within the United States, and Puerto Rico. The
frequency of estimates and availability of demographic detail vary by geographic level. The schedule of
releases are available at
http://www.census.gov/population/www/estimates/estsched.html.
Definition:
The Census Bureau's Population Estimates Program (PEP) produces July 1 estimates for years after the
last published decennial census (1990), as well as for past decades. Existing data series such as births,
deaths, Federal tax returns, medicare enrollment, and immigration, are used to update the decennial
census base counts. PEP estimates are used in Federal funding allocations, in setting the levels of
national surveys, and in monitoring recent demographic changes. A methodology reference
accompanies most of our population estimates offerings.
With each new issue of July 1 estimates, PEP revises estimates for years back to the last census.
Previously released estimates become superseded. Revisions to estimates are usually due to input data
updates, changes in methodology, or legal boundary changes.
Scope and Methodology:
County population estimates are created by starting with the most recent decennial census figure (April
1, 1990) and updating that figure with information on births, deaths, domestic migration (in/out flows with
other counties in the U.S.), and international migration (in/out flows with other countries) that have taken
place between the census date and the date of the population estimate. Birth and death data are
obtained through vital statistics, domestic migration is estimated through the address matching of federal
tax returns, and international migration data is supplied by the Immigration and Naturalization Service.
Resident population and net change
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