Unable to link observations across certain months using CPSIDP?


I am trying to use the CPSIDP variable to match individual observations across months but, for some reason, I am unable to do so across certain months in 1995. For example, I sorted my data by CPSIDP, Year and Month and created a variable that is 1 at month t if two observations have the same CPSIDP in month t and t+1. But, for example, between May 1995 and June 1995, I obtain no links (this indicator variable is equal to 0 for all observations in May 1995). This is weird because Drew et al says that you should get 95,000-100,000 matches across months back to at least 1994. Any help is appreciated!


The Census Bureau updated their sub-state geographic identifiers in September 1995, excluding them completely from the June-August 1995 period. As a result, they intentionally prevented the matching of households from samples with old geographic identifiers to samples with the new geographic identifiers. Specifically, it should be possible to link within the following three time periods, but not across:

  1. Prior to June 1995

  2. June-August 1995

  3. After August 1995

Hope this helps.