Archigos is a collaborative effort of Hein Goemans (University of Rochester), Kristian Skrede Gleditsch (University of Essex) and Giacomo Chiozza (University of California, Berkeley). For a detailed description of the data, please refer to the case description document, available at mail.rochester.edu/~hgoemans.
171 countries with at least one year of observation both in POLITY IV and Archigos 2.5, each for 1800-2003