In my last post from the distant past I explained the differences between the different types of census data and briefly discussed some of the limitations of the data-- that they underestimate certain populations that are often the focus of issues of equity: small population groups, those with no or unstable housing, and the incarcerated. But census data can still be a powerful tool for visualizing disparities.
Below I have created a map in Google MyMaps, a powerful tool that enables people who don't have Jedi-level GIS skills to create interactive maps that have editable data. The map shows the census tracts for Seattle (a census tract is the base geographic unit of measurement for the decennial census).
The tracts are numbered in a way that may repeat within a state, but not within a city. I created the map using a .kml version of the census tract boundary file. I created mine by downloading the .shp file version of the Seattle census from Seattle's Open Data site, http://data.seattle.gov/ and converting it to a .kml file in ArcGIS, but fortunately, the Seattle Open Data Site now also contains a .KML version of the file. There are also a number of good, free utilities to accomplish the conversion if you don't have access to ArcGIS or .KML files.
I also created a blank map of the Seattle Public-Use Microdata Areas (PUMAs), the base geographic unit of the American Community Survey (ACS) PUMS shown below.
Why do the decennial census and the ACS have different geographic units? No, it's not them being ornery; the reason is that the ACS isn't a true count-- rather it samples a subset of the population (I will in a later post discuss what this does to ACS estimates), and the PUMAs in every area of the country differ in order to encompass a sizable chunk of the population each year people are sampled.
Using the PUMA map and the census tract maps, we can begin to link geographic data with other administrative data that is available for the same geographic extents. By combining those data with information about groups that interest you, you will be able to get a better sense of where disparities exist.