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 ..