Missing Metropolitan Statistical Area in ACS 5 year extracts

Hello,

I’ve downloaded and cleaned 10 years’ worth of the ACS 5-year at the Census Block Group level using STATA. That said, I noticed that the variables having to do with metropolitan statistical area (CBAA for example) are empty. Differentiating urban and rural communities is pretty important for my project. Is there something I’m doing wrong? I can’t seem to find how to get these on the NHGIS website. Sorry if this is a silly question.

Best,

Chris

Hi Chris,

It’s not a silly question! Unfortunately, the geographic codes in the source ACS summary files from the Census Bureau are generally limited to the key identifying codes for a given level. Even though they certainly could identify the CBSA in which each block group is located, the CBSA field is left blank for block groups, and for all other levels that don’t include CBSAs in their hierarchy.

E.g., the “metropolitan division” level includes CBSAs as a parent level, so metropolitan division data will include CBSA codes. In county data, there are state codes because states are in the county hierarchy, but there are no CBSA codes, nor region or division codes, even though counties nest within those areas, too.

FWIW, the geographic info in decennial census summary files is more complete, providing codes for all containing units.

To get CBSA codes for ACS block group data, I think the most straightforward approach is to use the Census Bureau’s CBSA delineation files, joining them to the block group data based on the state and county identifiers.

Hi Jonathan,

Thank you so much for the response! I’m glad to know I wasn’t the problem (because I usually am). I’ve had a look at those delineations and I am curious if you konw if there is any crosswalking I need to do to convert the place codes from the Census Bureau into the codes used for the ACS 5-year. I believe the ACS 5 year I’m using are all in 2010 Tiger Lines. Thanks again!

Best,

Chris

To join CBSA delineation files with block group data, the key codes you need are the state and county FIPS codes. These codes are available in the delineation files and in pretty much any source of block group data, as a complete block group ID includes them. Standard block group IDs are formed as a concatenation of [state FIPS] & [county FIPS] & [census tract code] & [block group code].

A couple things to watch for:

  1. NHGIS “GISJOIN” codes include the state and county FIPS codes, but the GISJOIN version appends an extra digit, usually 0, after each FIPS code. (The extra digit is used to distinguish historical areas.)
  2. FIPS codes crucially include leading zeros. A proper state FIPS is exactly 2 digits (e.g., “04”) and a proper county FIPS is exactly 3 digits. Many software packages will automatically convert the codes from text strings to numbers, which drops the leading zeros. Just watch out for that, and make sure when you join two tables that they have matching code formats.