ePodunk uses three different products from the U.S. Census Bureau in its demographic profiles. The Population Overview reports for the year 2000 are drawn from the SF 1 file of the decennial census. This file is drawn from a "short form" that is distributed to every U.S. household and collects basic information on age, race, sex, and household type.
Other demographic reports for the year 2000 are based on the SF 3 file. These data are drawn from a "long form" that is distributed to roughly one in seven U.S. households and collects detailed information on social and economic characteristics such as income, ancestry, and housing. The sample of households that reported on these long forms is then weighted by the Census Bureau to produce estimates for the entire population in the SF 3 file. One consequence of the weighting procedures is that at smaller levels of geography, SF 3 population estimates can be slightly different than SF 1 numbers. Although the Census Bureau considers SF 1 to be the official source of population numbers, the SF 3 numbers are a much more detailed source of information about local areas.
ePodunk's 2005 numbers are drawn from the American Community Survey (ACS), which is similar to the long form. The ACS has been mailed to about 250,000 households a month since the beginning of 2005, and by 2010 its data on local areas will be so detailed enough that the long form will no longer be necessary. In the fall of 2006, ACS data were released for all counties, cities, and places in the U.S. that had populations of 65,000 or more. The data include 775 counties, and 492 cities. The ACS will be extended to all geographic entities in the U.S. and Puerto Rico with a population of 20,000 or more in 2008, and to every level of geography starting in 2011.
Use caution when comparing estimates from the 2005 American Community Survey (ACS) with the 2000 Census. Unlike the Census:
* ACS estimates only cover areas with more than 65,000 people.
* ACS estimates do not include people living in institutions.
* Each ACS estimate has a published margin of error. We only report estimates when the margin of error is less than +/- five percent. More information on ACS margins of error is available here.
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