Polity data series in the context of The Economist Democracy Index

Anocracy, or semi-democracy, is a form of government that is loosely defined as part democracy and part dictatorship, or as a "regime that mixes democratic with autocratic features". Another definition classifies anocracy as "a regime that permits some means of participation through opposition group behavior, but that has incomplete development of mechanisms to redress grievances." The term "semi-democratic" is reserved for stable regimes that combine democratic and authoritarian elements. Scholars distinguish anocracies from autocracies and democracies in their capability to maintain authority, political dynamics, and policy agendas. Anocratic regimes have democratic institutions that allow for nominal amounts of competition. Such regimes are particularly susceptible to outbreaks of armed conflict and unexpected or adverse changes in leadership.

The operational definition of anocracy is extensively used by scholars Monty G. Marshall and Benjamin R. Cole at the Center for Systemic Peace, and that definition was widely disseminated through the polity data series. This data set aims to measure democracy in different states and uses anocracy as one of its classifications for regime type. Consequently, anocracy frequently appears in democratization literature that utilizes the polity data set.

Electoral competition, political competition or electoral competitiveness describes the amount of competition in electoral politics between candidates or political parties, usually measured by the margin of victory.The Polity data series includes a measure of political competition. Political competitiveness can be affected by the proportionality between votes and seats, which can be represented by Gallagher index.