The NHGIS time series for poverty data are nominally integrated:
Nominally integrated tables link geographic units across time according to their names and codes, disregarding any changes in unit boundaries. The identified geographic units match those from each census source, so the spatial definitions and total number of units may vary from one time to another (e.g., a city may annex land, a tract may be split in two, a new county may be created, etc.). The tables include data for a particular geographic unit only at times when the unit’s name or code was in use, resulting in truncated time series for some areas.
There are missing values in cases where a tract number exists in some years and not in others. And the 111,000+ tract numbers are the total that have ever existed since the earliest year in the time series. (There should be around 73,000 tract numbers with valid data for 2010.)
NHGIS also has geographically standardized time series that provide data only for the ~73,000 2010 census tracts, including estimates for 1990 and 2000. But we don’t yet have poverty counts in those. If you’d like to generate 1990 and 2000 poverty data for 2010 tracts, you might consider using our geographic crosswalks.