search

uscensusbureau / api

empty repository solely used for API related issue tracking, bug reports and feature requests
https://census.gov/developers
6 stars 0 forks source link

Document geographic variants in GEOIDs #8

Open JoeGermuska opened 3 years ago

JoeGermuska commented 3 years ago

Data returned from data.census.gov and api.census.gov can include a GEO_ID value which is a key for linking data across queries, as well as linking to GIS data.

However, the structure of some of these GEO_IDs is obscure, and should be documented more clearly. There is a page, Understanding Geographic Identifiers (GEOIDs), which is a good start. However, the only mention it makes of the "geographic variant" is pointing out that it is 00 in an example GEO_ID.

However, for several geographies, the GEO_ID values returned have something other than 00 in that position.

There may be more; these are the ones I've found.

Whether in the API or some other source, there ought to be a complete enumeration of possible geographic variants with reference information about their sources. At a minimum, a reference from a given variant to a given TIGER vintage should be documented.

For CBSA/CSAs, which are formally delineated as lists of one or more counties, it would be valuable to be able to link the variant to a specific delineation. Experimentally, I've worked out that M5 is the Sep. 2018 delineation, and M4 is the Apr. 2018 delineation, but it ought to be systematically published.

For the State Legislative Districts, the API returns names which include a year in parentheses, and one can infer that L6 and U6 are the 2018 legislative year, and L5 and U5 are the 2016 legislative year, but, again, this ought to be made explicit.

loganpowell commented 3 years ago

Let me forward this to cedsci.feedback@census.gov to see what they say. Thank you for the detailed issue @JoeGermuska!

loganpowell commented 3 years ago

Just a heads up on this: The team is looking into it... it's been handed off deeper into the SME pools, so that's good. 🤞

loganpowell commented 3 years ago

@JoeGermuska Sorry for the delayed response. It looks like I missed a follow up made a couple of weeks ago:

We had quite a few emails between SMEs and BCs in GEO about this. It is in the works to create documentation for geographic variants, the work on that will start in a few months though. In the meantime below is some info and two attached files (for internal use/reference only). You (and us) can use these to answer questions, so please feel free to capture and summarize these details that work best for your responses.

Geographic variants are basically used for any geography that could have more than one vintage within a specific data year. The multiple vintages within a specific data year are usually associated with the decennial year (such as the retabulation of congressional districts throughout the decade against the 2010 Census, we have CD 111, 113, 114, etc. all available for 2010 data). However, this once did come in handy in a non-decennial data year. For the 2012 Economic Census, ECON wanted to publish their data using the new CBSA definitions. If you look at 2012 data, you'll see one variant for the 2012 ACS data and another for the 2012 Economic data.

For example, M6 is associated with the March 6, 2020, OMB delineations of the Core Based Statistical Areas, and will be used in the 2020 decennial data products. M5 is associated with the September 14, 2018 OMB delineations. But code M4 is associated with the August 15, 2017 OMB delineations. In addition to the list provided, they also apply to urban areas. Geographic variants are one of those things created last decade to support data releases by AFF for the way they published data for geographic areas that were retabulated using 2010 Census data throughout the decade as they were redefined.

In Appendix A, “Geographic Terms and Concepts,” there is a paragraph that describes what geographic variants ariants are. (But it doesn't include specific codes.) The first tech doc should be released around the same time that the PL 94-171 redistricting dataset is released. The Bureau’s web page on Metropolitan and Micropolitan Statistical Areas also has a link to the OMB Bulletins for Core Based Statistical Areas, and to the delineation files:

https://www.census.gov/programs-surveys/metro-micro.html

But these don’t make the connection to the MAF/TIGER vintage or the Geographic Variant code.

The Summary Levels Working Group is developing a document that defines the geographic variants more comprehensively. When this draft document is issued, the contents will be included in any public documentation that refers to geographic variants.

I will keep you looped in on the thread!