Information on County Transitions
This page contains Stata data files used to transition historical counties, county groups, and Public Use Microdata Areas (PUMAs) to 1990 counties. For details on the exact methods used to create these transition files, please refer to Burchardi et al (2019).
Each file contains a transition matrix in which each row represents a historic county or county group c and each column represents a 1990 county m. Each cell of the transition matrix takes a value that represents the fraction of the area of county c that is in 1990 county m. The first column in each file contains the county or county group identifier.
For historical counties (1880 to 1930) only one transition is needed, from the historical county to 1990 county. For 1970 and 1980, data is reported for county groups and so two transitions are needed: first the 1970 or 1980 county group needs to be transitioned to 1970/80 counties and second the 1970/80 county needs to be transitioned to the 1990 county. Finally, for 1990 through 2010 data is reported by PUMA and only one transition is required from PUMA to 1990 counties.