New answers tagged census
Taken from https://www.census.gov/geo/reference/gtc/gtc_bg.html Block Groups (BGs) are statistical divisions of census tracts, are generally defined to contain between 600 and 3,000 people... and Most BGs were delineated by local participants in the Census Bureau's Participant Statistical Areas Program. The Census Bureau delineated BGs only ...
Check out the geographic boundary change notes from the Census Bureau. I believe blocks, block groups and tracks' geometry are updated every 10 years with a new census. https://www.census.gov/geo/reference/boundary-changes.html Also checkout the User Notes from each year in the Tiger/line info https://www.census.gov/geo/maps-data/data/tiger-line.html
The one caution around using block group level data from the American Community Survey (which is a great resource!) is that the sample sizes are pretty small and you have to watch your margins of error, especially around things like median household income, which can be skewed in small populations. If you are interested in aggregating areas, here's one tool ...
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