Hello. I am very new to working with IPUMS U.S. census data files and GIS files, but I am experienced at using ArcGIS Pro, and I teach and heavily research U.S. census manuscript collections. I naively thought until tonight that IPUMS USA data sets and NHGIS data sets were the same thing, but couldn’t figure out why I had different views on each to find the data. I now understand that IPUMS USA is what you call census micro data (full count), and NHGIS is what you call summary data as well as the GIS files. I see how that CSV data sets I’ve downloaded NHGIS have the GISJOIN field, whereas CSV files from IPUMS USA do not.
Can I map IPUMS USA data to NHGIS GIS files? I think this older forum post says that we can manually create a GISJOIN field in IPUMS USA data sets, and then create the GISJOIN codes from particular jurisdiction codes (state, county, etc.). Is this process documented in any of the existing help literature, but I am just missing that? I am a librarian, so I’ve tried finding this answer in the help docs and in this forum, but am still unsure since I am so new to working with IPUMS.
Thank you for your help!
Colleen Robledo Greene
Digital Scholarship Librarian, California State University Fullerton
Dear Colleen,
The procedure I was mentioning for constructing GISJOIN fields is at the bottom of this page!
Best,
Daniele
1 Like
Hi Daniele.
Thanks for the quick reply. I understand that section now on the documentation you linked to and will give it a try.
Colleen
For the benefit of others reading the forum post, I am summarizing the guidance that Daniele helpfully linked above. As stated on the geographic tools page, IPUMS USA microdata can be joined to the IPUMS USA or IPUMS NHGIS GIS boundary files. The same steps provided at the bottom of the page for joining with NHGIS boundary files can also be used to construct GISJOIN codes for joining with the NHGIS summary data tables.
As you describe, while both IPUMS USA and IPUMS NHGIS release data derived from the ACS, the formats are different and there are different strengths and limitations of each. The microdata on IPUMS USA is best for running regression-style analyses with multiple variables, while IPUMS NHGIS is best for obtaining geographically precise aggregate estimates. There are certainly cases where using the two together can strengthen your analysis, but many users are able to get most or all of what they need from using just the microdata or just the summary files.