The PTS seeks to measure political terror. The authors define political terror as violations of basic human rights to the physical integrity of the person by agents of the state within the territorial boundaries of the state in question. It is important to note that political terror as defined by the PTS is not synonymous with terrorism or the use of violence and intimidation in pursuit of political aims. The concept is also distinguishable from terrorism as a tactic or from criminal acts.

The PTS measures levels of political violence and terror that a country experiences in a particular year based on a 5-level "terror scale" originally developed by Freedom House. The data used in compiling this index comes from three different sources: the yearly country reports of Amnesty International, the U.S. State Department Country Reports on Human Rights Practices, and Human Rights Watch's World Reports.