選舉制度影響政黨體系，是廣為人知的因果推論。依此邏輯，若以政黨體系為因，以選舉制度的變化為果，即產生內生性的選制變遷理論。然而，某些研究者仍認為選制變革起於和政黨體系無關的外生因素。本文主張，選制變遷是否受到政黨體系的影響，取決於選制的種類。第一，有利大黨的多數決選制如果始終未出現一黨過半，則國會屬於多黨制，有可能因為小黨組成多數聯盟而改採比例性選制。尤其當現狀為並立式單一選區兩票制時，可能因為小黨的議席多來自政黨名單，而比代表區域主義的多數決選制更容易導致..

It is well known that electoral system shapes party system. By this logic, an endogenous explanation for changes in electoral systems should treat party system as the cause and changes as the consequence, in sharp contrast with theories attributing changes to exogenous factors that are irrelevant to party system. This paper argues that whether changes in electoral system are caused by party system depend on the type of the electoral system. First, if a majority party never emerges from a majoritarian electoral system, minor p..

本文檢視全世界民主國家在不同總統與國會選制的搭配組合下，政黨體系有何不同。本文發現，就國會選制而言，國會選舉採比例代表制的國家， 其國會有效政黨數在整體上明顯多於國會選舉採單一選區相對多數制的國家;而不論是國會選舉採比例代表制或是採單一選區相對多數制的國家，有總統直選制度之國家的國會有效政黨數，明顯少於無總統直選制度的國家。 進一步言，在國會選舉採比例代表制的國家中，若總統選舉採相對多數制，其國會有效政黨數會少於總統選舉採兩輪決選制的國家;不過，在國會選舉採..

This study comprehensively observes the party system under different collocations of presidential and parliamentary electoral system in democracies all over the world. Regarding parliamentary electoral system, it is found that the effective number of parliamentary parties in the countries adopting proportional representation system(PR), overall, is apparently larger than that in countries adopting plurality with single-member-district system(SMD), and that in countries holding direct presidential elections is clearly smaller ..