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Theoretical Expectations and Actual Outcomes of Electoral Systems: How to Measure the Size of the Deviation?

Miroslav Nemčok and Jakub Šedo
From the journal World Political Science


The article criticises current conceptual frameworks focused on the evaluation of the performance of electoral systems. It offers a new tool allowing researchers to measure the size of the deviation of electoral outcomes from theoretical expectations. The index d=log[NS/(MS)1/6] is built on the Seat Product (Taagepera, Rein (2007b) Predicting Party Sizes: The Logic of Simple Electoral Systems. New York: Oxford University Press) and captures the deviations of electoral outcomes from predictions solely on the basis of two institutional factors – average district magnitude (M) and size of assembly (S). The theoretical background of index d is explained, and its reliability is further supported by conventional econometric methods based on empirical data.


Table A1:

List of Included Elections.

Czech Republic19901992199619982002200620102013
New Zealand194619491951195419571960196319661969
South Africa19941999200420092014


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Article note

This article was written at Masaryk University with the support of the Specific University Research Grant provided by the Ministry of Education, Youth and Sports of the Czech Republic.

Published Online: 2018-11-03
Published in Print: 2018-10-25

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