In this document, the author proves that, as consociational theories suggest it, proportional electoral systems are most likely to facilitate accommodation between ethnic groups, making them more suitable for transitional and consolidating democracies. The first part summarizes the key assumptions in consociational theories of democracy. The second one describes the research design and methods. Part III defines and analyzes the primary ethnic cleavages in several societies. The conclusion considers the lessons of these findings for issues of effective electoral designs and conflict mediation through constitutional engineering.