Abstract: Three types of political regimes are evaluated for their success in establishing stable and durable democracies. These are parliamentarism with majority electoral rules, parliamentarism with proportional representation, and presidentialism. An empirical analysis of the 123 attempts to establish democratic regimes in countries with more than one million inhabitants since the nineteenth century shows that parliamentarism with proportional representations is the formula with highest rates of success. This empirical finding supports the hypothesis that pluralistic political institutions have higher capability to produce socially efficient outcomes and obtain endogenous support.

Keywords: democracy, democratization, parliamentarism, pluralism, political stability, presidentialism, proportional representation, social efficiency,