data sources

Info about any spatial or attribute data sources

Downloading Data for Small Census Geographies in Bulk

I needed to download block group level census data for a project I’m working on; there was one particular 2010 Census table that I needed for every block group in the US. I knew that the American Factfinder was out – you can only download block group data county by county (which would mean over 3,000 downloads if you want them all). I thought I’d share the alternatives I looked at; as I searched around the web I found many others who were looking for the same thing (i.e. data for the smallest census geographies covering a large area).

The Census FTP site at http://www2.census.gov/

This would be the first logical step, but in the end it wasn’t optimal based on my need. When you drill down through Census 2010, Summary File 1, you see a file for every state and a national file. Initially I thought – great! I’ll just grab the national file. But the national file does NOT contain the small census statistical areas – no tracts, block groups, or blocks. If you want those small areas you have to download the files for each of the states – 51 downloads. When you download the data you can also download an MS Access database, which is an empty shell with the geography and field headers, and you can import each of the text file data tables (there a lot of them for 2010 SF1) into the db and match them to the headers during import (the instructions that were included for doing this were pretty good). This is great if you need every variable in every table for every geography, but I was only interested in one table for one geography. I could just import the one text file with my table, but then I’d have to do this import process 51 times. The alternative is to use some Python to get that one text file for every state into one big file and then do the import once, but I opted for a different route.

The NHGIS at https://www.nhgis.org/

I always recommend this resource to anyone who’s looking for historical census data or boundary files, but it’s also good if you want current data for these small areas. I was able to use their query window to widdle down the selection by dataset (2010 SF1), geography (block groups), and topic (Hispanic origin and race in my case), then I was able to choose the table I needed. On the last screen before download I was able to check a box to include all 50 states plus DC and PR in one file. I had to wait a couple minutes for the request to process, then downloaded the file as a CSV and loaded it into my database. This was the best solution for my circumstances by far – one table for all block groups in the country. If you had to download a lot (or all) of the tables or variables for every block group or block it may take quite awhile, and plugging through all of those menus to select everything would be tedious – if that’s your situation it may be easier to grab everything using the Census FTP.

nhgis

UExplore / Dexter at http://mcdc.missouri.edu/applications/uexplore.shtml

The Missouri Census Data Center’s UExplore / Dexter tool lets you choose a dataset and takes you to a window that resembles a file system, with a ton of files in it. The MCDC takes their extracts directly from the Census, so they’re structured in a similar way to the FTP site as state-based files. They begin with the state prefix and have a name that indicates geography – there are files for block groups, blocks, and one for everything else. There are national files (which don’t contain small census areas) that begin with ‘us’. The difference here is – when you click on a file, it launches a query window that let’s you customize the extract. The interface may look daunting at first, but it’s worth exploring (and there’s a tutorial to help guide you). You can choose from several output formats, specific variables or tables (if you don’t want them all), and there are a bunch of handy options that you can specify like aggregation or percent totals. In addition to the complete datasets, they’ve also created ‘Standard Extracts’ that have the most common variables, if you want just a core subset. While the NHGIS was the best choice for my specific need, the customization abilities in Dexter may fit your needs – and the state-level block group and block data is conveniently broken out from the other files.

Lastly…

There are a few others tools – I’ll give an honorable mention to the Summary File Retrieval tool, which is an Excel plugin that lets you tap directly into the American Community Survey from a spreadsheet. So if you wanted tracts or block groups for a wide area for but a small number of variables (I think 20 is the limit) that could be a winner, provided you’re using Excel 2007 or later and are just looking at the ACS. No dice in my case, as I needed Decennial Census data and use OpenOffice at home.

ACS Trend Reports and Census Geography Guide

I recently received my first question from someone who wanted to compare 2005-2007 ACS data with 2008-2010. With the release of the latter, we can make historical comparisons with the three year data for the first time since we have estimates that don’t overlap. We should be able to make some interesting comparisons, since the first set covers the real estate boom years (remember those?) and the second covers the Great Recession. One resource that makes such comparisons relatively painless is over at the Missouri Census Data Center. They’ve put together a really clean and simple interface called the ACS Trends Menu, which allows you to select either two one period estimates or two three period estimates and compare them for several different census geographies – states, counties, MCDs, places, metros, Congressional Districts, PUMAs, and a few others – for the entire US (not just Missouri). The end result is a profile that groups data into the Economic, Demographic, Social, and Housing categories that the Census uses for its Demographic Profile tables. The calculations for change and percent change for the estimates and margins of error are done for you.

Downloading the data is not as straightforward – the links to extract it just brought me some error messages, so it’s still a work in progress. Until then, a simple copy and paste into your spreadsheet of choice will work fine.

ACS Trends Menu

If you like the interface, they’ve created separate ones for downloading profiles from any of the ACS periods or from the 2010 Census. The difference here is that you’re looking at one time frame; not across time periods. The interface and the output are the same, but in these menus you can compare four different geographies at once in one profile. Unlike the Trends reports, both the ACS and 2010 Census profiles have easy, clear cut ways to download the profiles as a PDF or a spreadsheet. If you’re happy with data in a profile format and want an interface that’s a little less confusing to navigate than the American Factfinder, these are all great alternatives (and if you’re building web applications these profiles are MUCH easier to work with – you can easily build permanent links or generate them on the fly).

The US Census Bureau also recently put together a great resource called the Guide to State and Local Census Geography. They provide a census geography overview of each state: 2010 population, land area, bordering states, year of entry into the union, population centroids, and a description of how local government is organized in the state – (i.e. do they have municipal civil divisions or only incorporated cities and unincorporated land, etc). You get counts for every type of geography – how many counties, tracts, ZCTAs, and so on, AND best of all you can download all of this data directly in tab delimited files. Need a list of every county subdivision in a state, with codes, land area, and coordinates? No problem – it’s all there.