Duverger's law versus the cleavage approach: Testing competing theories of party systems in new democracies

This dissertation is a quantitative analysis of party systems in the so-called third-wave new democracies in Latin America, Southern and Eastern Europe, and Asia. It examines how institutional (electoral systems) and structural (social cleavages) factors affect the development of party systems in perspectives of the number of parliamentary parties, inter-party structures, the relative strength of parties to non-partisan independents, and the institutionalization of party systems.; The regression results demonstrate that both institutional and structural factors matter in the formation of party systems, though the former seems to be more powerful. While the impact of structural factors on party systems is largely stable, the consequences of electoral systems for party systems are much more complex than what is usually assumed. Proportional representation (PR) electoral formulas and large districts have a double-edged effect on the number of parties on the one hand, and their multiplying power is usually conditioned by other variables on the other.; A Single-member district (SMD)/the first party and PR/multipartism rather than Duverger's SMD/bipartism and PR/multipartism dichotomy is found in the analysis of inter-party structures in new democracies, showing that the main difference between SMD and PR is their bias for/against the dominant party. The analysis of non-partisan independents in new democracies suggests that mixed electoral systems and presidential systems may lead to non-partisan independents. The regression results of institutionalization of party systems indicate that the electoral rules that encourage spatial voting such as PR and large assemblies may help institutionalize party systems, while those that encourage strategic voting such as thresholds may destabilize party competition.; It is argued that careful design of electoral institutions can help strengthen parties and institutionalize party systems, and thus, smooth democratic transitions in the transforming third-world countries.