This variable codes the number of leader transitions in the year of reference. The authors rely on existing data by Goemans, Gleditsch, and Chiozza (2009) to determine leaders and leadership changes. This database (Archigos v. 4.1 for the 5th version of this dataset) identifies the effective primary ruler and the dates the leader was in power for each independent state, as coded by Gleditsch and Ward (1999), between 1875 and 2014.

The authors code the leader transition as occurring on the day the new leader assumes power. Thus, if one leader departs from office in December and the new leader takes power in January, the leader who left office in December will continue to be listed as the first leader in January until the transition occurs.