Joining Census Data from American FactFinder to TIGER/Line 2012 Shapefiles
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Doing demographic research has gotten a whole lot easier over the last years. U.S. Census now offers their TIGER/Line data in ArcGIS shapefile format, Census data and estimates from the American Community Survey are readily available through American FactFinder, and it's all free and available on the internet.
20 years ago or so as a graduate student at the University of California, I was doing environmental justice research in Silicon Valley. It wasn't an easy task. I had to download census data from the University of California super computer in San Diego. Even earlier, I had to get the data on magnetic tape.
TIGER/Line geodata was available, but not in a format that was easy to use. I didn't have the time to learn how to convert these to shapefile format, so, blessed with a bit of funding, we purchased these very expensive shapefiles from a private vendor. Now this has all changed.
On August 17, 2012 Census released the 2012 TIGER/Line data. These GIS files include all sorts of boundaries; line features like roads, streams; polygons like census tracts, block groups, blocks; and much more. An Amazing amount of geodata. You can download these in shapefile format.
But, there's still some work to do. The TIGER/Line shapefiles do not have demographic census data included with them. You must join this data to the shapefiles yourself or have someone like me do it for you. The census data is readily available for download at American FactFinder. It includes data from the decennial census as well as current and future estimates based on data from the American Community Survey.
U.S. Census published, Downloading Data from the New American FactFinder to use with TIGER/Line Shapefiles (1.2MB PDF format). This document steps you through the process of making the fields (GEOID10) in each data set identical so that the join will be successful. I've found that older versions of MS Excel won't handle some of the larger downloads (CSV format) from American FactFinder, but I have found that Open Office Calc handles them just fine.
Once you get into the how-to document mentioned above, you'll learn how to convert existing GEOID fields into the format required for the join. Maptitude is my GIS of choice (click here to learn why I prefer Caliper's Maptitude). I noted that the tutorial uses Excel and I found that Calc does the "text to column" operation as well. You'll find it under the "data" menu item. Make sure that you use a capital "S" as the separator and it should work just fine. One problem. I found that it would not make the join until I went back into Calc and reformatted the new GEOID column's cells as "text" and made sure it was aligned "left."
Census has provided TIGER/Line Shapefile technical documentation that you can download here (4.6MB PDF format).
If you need help with custom shapefiles and/or GIS projects using demographic or other data, send me an email and we'll discuss it.
MapCruzin has been online since 1996 and we've been creating GIS shapefiles for 25 years.
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