For the 100th-102nd congresses, the year listed in the total pop dataset is 1990. Should this be based on 1980?

The census years do not seem to match up with the congresses. For example, for the 95th-97th congress and 98th congress datasets, the year is 1980, which is correct (not actually for the 95th and 96th congresses, which should have the year 1970, but I’m starting with the 97th congress so this is fine for my purposes). But for the 100th-102nd congresses, the year listed in the dataset is 1990. So is this based on the 1990 census? These all should still be based on the 1980 census no?

The same is true for the 106th and 107th congresses. The year listed in the dataset is 2000 but these should still be based on the 1990 census.

NHGIS data for congressional districts relate to years in different ways.

One set of years describes the “geographic vintage”, the period over which the congressional districts were legally in use. E.g., districts for the 100th-102nd Congresses were legally in effect for years 1987-1993.

Another year–the year noted in NHGIS dataset labels–describes the _census year_ for which summary data were tabulated for the districts. E.g., the only census year with summary data reported for the 100th-102nd congressional districts is 1990.

It’s also true that the definitions of 100th-102nd congressional districts were _based_ on 1980 population totals, but the standard Census Summary Tape Files, from which NHGIS derives its data, do not include any 1980 data for these districts, only 1990 tables. Therefore, NHGIS has 1990 data for these districts, but not 1980 data.