Polity data series
The Polity data series is a widely used data series in political science research. The latest version, Polity IV, contains coded annual information on the level of democracy for all independent states with greater than 500,000 total population and covers the years 1800–2011. Polity's conclusions about a state's level of democracy are based on an evaluation of that state's elections for competitiveness, openness and level of participation. For each year and country, a "Polity Score" is determined which ranges from -10 to +10, with -10 to -6 corresponding to autocracies, -5 to 5 corresponding to anocracies, and 6 to 10 to democracies.
The 2002 paper "Conceptualizing and Measuring Democracy" claimed several problems with commonly used democracy rankings, including Polity, opining that the criteria used to determine "democracy" were misleadingly narrow.
- Casper, Gretchen, and Claudiu Tufis. 2003. “Correlation Versus Interchangeability: the Limited Robustness of Empirical Finding on Democracy Using Highly Correlated Data Sets.” Political Analysis 11: 196-203.
- Gerardo L. Munck, Jay Verkuilen (Vol. 35 No. 1, February 2002 5-34), "Conceptualizing and measuring democracy: Evaluating Alternative Indices", Comparative Political Studies (Sage Publications)