I want to use the distribution of family income by race at the tract-level to calculate a measure of income segregation in metro areas by race between 1970 and 2000. I’ve identified the correct data tables for 1970, 1980, and 2000, but I can’t figure out where the table for 1990 is. I understand that racial breakdowns were not included in the summary tape files 3 in 1990, but previous research has said they found this measure at the tract-level in the summary tape files 4a in 1990. STF 4a (as well as 4b) on IPUMS doesn’t have tract-level tables available, though. Am I missing something, or is the table I’m looking for in 1990 simply not available?
Tract data are available in IPUMS NHGIS 1990 STF 4 datasets, but not via the “standard” tract geographic level.
At the standard census tract level, each data record corresponds to a single, whole tract. NHGIS identifies this level as “Census Tract (by State–County)”.
The original 1990 STF4 files supply no data at the standard tract level. Instead, STF4 provides data for two “compound” tract levels:
“Census Tract/Block Numbering Area (by State–County–Metropolitan Statistical Area/Consolidated Metropolitan Statistical Area/Remainder–Primary Metropolitan Statistical Area/Remainder)”
“Census Tract/Block Numbering Area (by State–Metropolitan Statistical Area/Consolidated Metropolitan Statistical Area/Remainder–Primary Metropolitan Statistical Area/Remainder–County–Place [10000 or more persons]/Remainder)”
For the first of these levels, nearly all of the data records describe whole tracts, except for a few cases in New England where a single tract straddles metropolitan area boundaries. In those cases, there are separate data records for the parts of the tract lying in each metro area. (The second compound tract level in 1990 STF4 divides tracts by metro area boundaries _and_ by place boundaries, so it includes many more tract subparts. If you’d prefer whole-tract data, the first level is a better starting point.)
To find compound levels in the NHGIS Data Finder, click on SHOW COMPOUND LEVELS in the upper right of any geographic level selection window.
(If you’re in the GEOGRAPHIC LEVELS Filter pop up, you’ll also need to select a non-default category of geographic levels on the left. The default selection of MOST POPULAR omits compound levels. The ALL and SMALL AREA STATISTICAL UNITS categories include compound tract levels.)
Also, if you ever want to know which geographic levels are covered in a particular NHGIS dataset, first find a table from that dataset in the SELECT DATA grid, and then click on the dataset code in the YEAR - DATASET column. A DATASET DETAILS window will pop up that lists (among other things) all geographic levels available for the dataset, including compound levels.