NOTE: Data are available for some areas, such as Baltimore City with a population of over 600,000, for all three data releases (annual, three-year and five-year). For Kent County, however, with a population of just over 20,000, data are available for three-year and five-year releases only. Data from the different releases should not be mixed, however, so if a comparison of median household income between Baltimore City and Kent County is needed for example, one would have to use the same data set - the three or five-year data for Baltimore City and Kent County to be consistent.
The Census Bureau collects ACS data from a sample of the housing unit addresses in the United States --rather than from the whole population All ACS data are survey estimates. To help you interpret the reliability of the estimate, the Census Bureau publishes a margin of error (MOE) for every ACS estimate.
American Community Survey 1-, 3-, and 5-year estimates are period estimates, which means they represent the characteristics of the population and housing over a specific data collection period. Data are combined to produce 12 months, 36 months or 60 months of data. These are called 1-year, 3-year and 5-year data.
For more information on the ACS and how to use it: See these instructional Power Point presentations and Census Documents
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