Cathy Michael
Understanding Geographic Level Data
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Geographic Hierarchy Diagram-U.S. Census BureauThis diagram shows how levels of geography relate from the National level down to Census Blocks.
Metropolitan Statistical Area (MSA) -Cities and surrounding areas of 50,000 people or more
Tracts- 1,200-8,000 people with an optimum of 4,000
Block Groups - 600-3,000 people. Block groups usually have between 250 and 550 housing units. Block Groups are the smallest area for which American Community Survey (ACS) data are collected and published.
Blocks -Census blocks, the smallest geographic area for which the Bureau of the Census collects and tabulates decennial census data, are formed by streets, roads, railroads, streams and other bodies of water, other visible physical and cultural features, and the legal boundaries shown on Census Bureau maps.
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Census GeocoderThe Census Geocoder is an address look-up tool that allows the user to submit a single address, batch of up to 10,000 addresses, or location coordinates for geocoding. This will give information for an address such as county, track, block group, block.