I am trying to make tract-level thematic maps for several indicators (e.g. unemployment, median family income etc.).
In the KML and SVG files I am using (including that obtained from TIGER) the 11 digit GeoID10 seems to be the best column through which I can merge data pertaining to the census tracts either by using the "GEO.id2" field from ACS data downloaded as CSV from FactFinder or through a concatenation of "state","county","tract", fields retrieved via the API.
Is there a different key I should be using for tract-level data? This seems to work when making chloropleth maps using the same methods used for making US county-level thematic maps with FIPS (as seen here http://flowingdata.com/2009/11/12/how-to-make-a-us-county-thematic-map-using-free-tools/ )
Thanks in advance for any help.