Thematic Mapping of Small Area ACS 5yr. Estimate Data and Census 2010 Data; Tips for Utilizing Census Products in your GIS May 2011. Items covered in this Presentation:. 1. American Community Survey (ACS) data use guidance; ACS vs. 2010 Census.
*** This is where to start for using Census data in GIS.
Data products are released in the year following the single year or multiyear period in which data are collected. ACS data includes median home value, median income, percent foreign-born, percent without health insurance, etc. This type of demographic data for small areas (down to tract and block group for the 5yr data) has not been released from Census since the 2000 long form data releases. This data replaces the data formerly collected via the Census long form.
Download tabular data from American Fact Finder (AFF). The legacy AFF system will be phased out in 2011, but new AFF does not have 2005-2009 ACS 5yr estimates. All 2010 data is in new AFF, and all future data releases will be in new AFF.
You may need to calculate a new value for your map. In this example, I am dividing estimated number of persons living in poverty by the total estimated persons, and multiplying by 100 to get the percent living in poverty. Oftentimes I’ve found it is easier to calculate values for new values outside of GIS software.
To join your tabular data to the shapefile you use versions of the GEO_ID field:In the tract shapefile – CTIDFP00In the ACS data table – GEO_ID2
Much care should be used when deciding on thematic cartographic symbolization, and categorization of data. Consult Thematic Cartography texts/experts as needed. For the poverty map, I considered different classification breaks, and opted for the Jenks classification on the left.