More on Measuring Two-Party Competition: A Response to Dunleavy

Abstract

Gaines and Taagepera [(2013) How to operationalize two-partyness. Journal of Elections Public Opinion and Parties, 23(4), pp. 387 -404] propose two indices of two-party competition for district-level data, both of which are alleged to be flawed. The case against them rests mainly on whether or not elections with one dominant party should be regarded as exhibiting one-or two-way competition. For those inclined to see 90 -10% and 50 -50% outcomes are different in kind, our indices can provide better measures than the popular effective number of parties or the "gap". We agree that assessment of a set of outcomes, in a given election or over time, requires careful attention to the important distinction between microlevel data and aggregate measures.

Analysis of party systems by measures of concentration of inequality and asymmetry of the Pareto curve

“…Currently, the most widely used measure in political science for the state of party systems based on election results is the "effective number of parties, Eff NP" introduced by Laakso and Taagepera. The conceptual idea of the Eff NP and its varieties (Dunleavy & Boucek, 2016;Gaines & Taagepera, 2014;Golosov, 2010;Molinar, 1991;Rae, 1967;Taagepera, 1999) is to combine the number and size distribution of parties into a single fragmentation factor equal to the number of "important parties. "…”

Analysis of Party Systems by Measures of Concentration of Inequality and Asymmetry of the Pareto Curve

“…Currently, the most widely used measure for the fragmentation of party systems based on election results is the "effective number of parties, ENP" introduced by Laakso and Taagepera. The conceptual idea of the ENP and its varieties (Dunleavy & Boucek, 2016;Gaines & Taagepera, 2014;Golosov, 2010;Molinar, 1991;Rae, 1967;Taagepera, 1999) is to combine the number and size distribution of parties into a single fragmentation factor equal to the number of "important parties." The advantage of the ENP is the simplicity of calculations, while the disadvantage is the ambiguity in measuring party systems, since different scenarios for the distribution of votes in elections can correspond to the same value of the ENP.…”

Analysis of party systems by measures of concentration of inequality and asymmetry of the Pareto curve

“…Currently, the most widely used measure for the fragmentation of party systems based on election results is the "effective number of parties, ENP" introduced by Laakso and Taagepera. The conceptual idea of the ENP and its varieties (Dunleavy & Boucek, 2016;Gaines & Taagepera, 2014;Golosov, 2010;Molinar, 1991;Rae, 1967;Taagepera, 1999) is to combine the number and size distribution of parties into a single fragmentation factor equal to the number of "important parties." The advantage of the ENP is the simplicity of calculations, while the disadvantage is the ambiguity in measuring party systems, since different scenarios for the distribution of votes in elections can correspond to the same value of the ENP.…”