The POLITY3D dataset was collected using the POLITY3 data as a baseline, but added to that specific dating information about each polity change to allow for better temporal calibration with other datasets.
In collaboration with Keith Jaggers and Ted R. Gurr, the authors of a 1996–97 article added more accurate start and end dates to the Polity III data as they were available at that time. The dataset that was used in that article is still available on http://privatewww.essex.ac.uk/~ksg/polity.html
The coding sheets for the dating decisions were scanned in early 2004, and are now publicly available as a compressed set of PDF files.
Each file contains one or more pages for a polity change. Note that the project at the time was called 'Polity IV'; the name later changed to Polity IIId (d for 'dates'). The first line gives the first name of the coder (cf. the list of article authors), the coding date, and the case no. (CN, up to five digits).
The files are sorted in folders; first by region (Africa, The Americas, Asia, Europe, Oceania) and then by state name.
The number in parenthesis following the CN is the country number, according to the Correlates of War State System Membership list.
Please see the Polity IIId (3D) section on Kristian Gleditsch's POLITY Data Archive page for the latest version of these data and the codebook.
If you want to identify a certain regime change, go to the Polity IIId archive first, find the case no., and then open the corresponding pdf file from the set provided here.
For further information on these documents, please contact Håvard Hegre.