effective_number_of_parties: Effective Number of Parties (ENP)

In albuja/electoral: Allocating Seats Methods and Party System Scores

Effective Number of Parties (ENP)

Description

Computes the effective number of parties. The effective number of parties is a concept introduced by Laakso and Taagepera (1979) which provides for an adjusted number of political parties in a country"s party system. The idea behind this measure is to count parties and, at the same time, to weight the count by their relative strength.

Measuring how many parties, weighted according to size, are in a party system in a given election, the effective number of (electoral/legislative) parties is calculated employing the following formula:

ENP = 1 / sum(pi^2)

where pi is the share of votes/seats of the ith party.

A new approach developed by Golosov, Grigorii V. "The Effective Number of Parties: A New Approach" (2010) (http://ppq.sagepub.com/content/16/2/171.abstract) is also available.

Developed by Jorge Albuja Delgado ([e-mail]).

Usage

enp(votes, method)

Arguments

votes	vector of number/share of votes/seats per party
method	string to choose from c("Laakso-Taagepera", "Golosov"). Defaults to "Laakso-Taagepera"

Value

<<<<<<< HEAD A single numeric with the effective number of parties (ENP) value. ======= A single numeric with the effective number of parties value. >>>>>>> 1e569c45b115684281e88833fa245b2c223ee30a

Examples

enp(votes = c(94545, 74162, 25273))
enp(votes = c(94545, 74162, 25273), "Golosov")

albuja/electoral documentation built on Feb. 7, 2023, 5:12 a.m.