對選舉制度與選舉結果不比例性的關係，從事跨國的比較研究，是目前學術界的重點之一。可是，這些研究對選舉制度諸變數的概念在界定、運作化與分類上，以及在方法論上均有問題，本文旨在檢討現有跨國性比較研究文獻的缺失。 在選舉區層次，選舉制度的變數，如當選規則、選舉區規模與法定門檻等概念，相當明確。但在全國層次，因涉及在一國之內有數個選舉區或採雙層選舉區制，故學者們試圖建構：(1)全國層次的當選規則，(2)平均的或有效的選舉區規模，(3)有效的門檻等概念，作為全國層次選舉制度的變數。不過，本文研究發現：這些概念在界定、運作化與分類等方面都有爭議；而且學者們所從事的跨國性比較研究，在方法論上也有明顯的缺失；再者，當選規則與選舉區規模，對全國層次選舉結果不比例性的影響屬次要因素，只有間接作用。因此，筆者不得不說，現有關於選舉制度對選舉結果不比例現象之跨國性比較研究，所得知識存有瑕疵，研究方向似須改弦更張。 在本文結論中，筆者建議：針對現有研究缺失尋求改進之道，應先找出在全國層次影響選舉結果不比例性的可能因素。

Cross-countries studies of the disproportionality of various elec-toral systems have become a popular topic in academic circles. How-ever, the definition, operationalization, and classification of electoral system variables have methodological flaws. This paper will examine the deficiencies of previous Cross-countries studies. Concepts concerning electoral districts, such as electoral formula, district magnitude, and legal thresholds are fairly clear. However, at the national level, the electoral system may include many electoral districts or dual electoral levels. Because of this, scholars have constructed 1) national electoral formula, 2) average or effective dis-trict magnitude, and 3)effective threshold. Still, the definition, operati-onalization, and classification of these concepts have all been criticized. In addition, when used in Cross-countries studies there have been glaring methodological errors. Furthermore, at the national level, electoral formula and district magnitude have only limited influence on disproportionality. In this light, existing Cross-countries studies of electoral disproportionality are flawed and must be improved. In this paper I propose that the best method for this lies primarily in the identification of possible influences on electoral disproportional-ity at the national level.