In a comprehensive and systematic examination of democratic legislatures, Taagepera and Shugart (1989) develop a "generalized Duverger's Rule." In an exhaustive empirical analysis they find a positive relationship between district magnitude and the size

Falling into a Niche: Institutional Equilibrium between Plurality and Proportional Representation for Large Political Parties" Scholars of electoral systems (e.g., Duverger, 1954; Rae 1967) argue that a combination of electoral system and district magnitude provide the strategic incentives for political party competition. All electoral systems reward large parties with a disproportional seat bonus, with this bonus being more pronounced in plurality/majority systems. Thus, large parties invariably wish to compete in majoritarian systems while smaller parties seek a proportional system of seat allocation. This paper shows that an institutional "niche" develops in some party systems where the second-largest party prefers the current electoral system over either a more proportional or more majoritarian system. Specifically, I illustrate how parties in Irish, Tasmanian, Australian House and Australian Senate elections occupy such an equilibrium. Vote transfers create a seat bonus that does not exist in either more proportional or more majoritarian systems (e.g., the Single Non-Transferable Vote).