Ever wonder about the statefp and statefp10 codes in the census block files?

I’ve always wondered about the statefp and statefp10 columns in the census block shape files.  I’m pretty sure they mean that some census blocks belong to different states in 2010 vs 2013.  Whether the LEGALLY belong to another state or not, I don’t know.

I’ve never investigated this state switching until now.  I put all the 2013 blocks into a PostGIS database, ran pgsql2shp with the query “SELECT * FROM tracts WHERE statefp != statefp10”, and visualized it in GeoCanvas.

Phase changes

Phase changes

We can see that all of them are on state lines (duh) and that are mostly in the middle of the country.  There’s nothing on the West Coast but there’s something a little something between Pennsylvania and Ohio.  He’s a close up of that with a different rate of extrusion.  It looks like 6 different shapes…

Screen Shot 2013-12-08 at 10.30.41 PM

Let’s give it some context and see if it reveals anything else and with 3 clicks in GeoCanvas we can make it transparent, turn on outlines, and add a beautiful basemap.

Screen Shot 2013-12-08 at 10.39.40 PM

Notice how the change lines follow the shape of the roads. Interesting! I bet there’s a story behind this stuff.