Effective number of parties (seats; Taagepera 1997)

Quick info
Data type	Numeric
Scale	Metric
Value labels	Not applicable
Technical name	polnat_politics_taag97_seats
Category	Political factors
Label	Effective number of parties based on seat share (Taagepera 1997)
Related indicators	Effective number of parties (votes; Laakso & Taagepera 1979) Effective number of parties (seats; Laakso & Taagepera 1979) Effective number of parties (votes; Taagepera 1997) Effective number of parties (votes; Golosov 2010) Effective number of parties (seats; Golosov 2010) Election date lower legislative chamber

This indicator displays the effective number of parties in the 1st or lower legislative chamber based on seat share according to the estimation formula proposed by Laakso and Taagepera 1979, but with Taagepera 1997 adjustment for incomplete data.

Conceptually, the motivation is that "[i]n the presence of a large lumped category of 'Other' parties the effective number of parties cannot be known exactly" (Taagepera 1997, 145). For this reason the original formula is amended by making assumptions about the distribution of seats among the unknown number N of "other" parties. The "least component approach" applied for this indicator hereby is the average of the upper and lower boundary taking the possible range of N into account (for more details see Taagepera 1997, 147-148).

Coding rules

• If the total seat share of an election covered in the sources was < 60%, the effective number of parties is not estimated as it tends to be heavily distorted.
• According to V-Party's (Lührmann et al. 2020) and Elections Global' (Döring and Düpont 2020) coding rules only parties with a vote share >= 5% are included. This may slightly alter the estimate compared to other data collections that try capturing parties down to the promille level. However, the issue is less relevant for this indicator based on the seat share because parties with a vote share >= 5% usually are among the smaller ones in parliament and the total seat share covered is always higher than the total vote share per election in the sources. Furthermore, for elections with a large, missing total seat share the issue is less relevant for this indicator than for the original one which ignores the category "others".
• Missing countries in V-Party are complemented by data from Elections Global.
• Data is available for election years only.

Bibliographic info

Citation: Taagepera, Rein. 1997. "Effective number of parties for incomplete data." Electoral Studies 16 (2): 145–51. https://doi.org/10.1016/S0261-3794(97)00003-6

Related publications:

• Döring, Holger, and Nils Düpont. 2020. "Elections Global: Election results in 207 countries, 1880–2015". Harvard Dataverse, V2. https://doi.org/10.7910/DVN/OGOURC
• Laakso, Markku, and Rein Taagepera. 1979. "'Effective' Number of Parties." Comparative Political Studies 12 (1): 3–27. https://doi.org/10.1177/001041407901200101
• Lührmann, Anna, Nils Düpont, Masaaki Higashijima, Yaman Berker Kavasoglu, Kyle L. Marquardt, Michael Bernhard, Holger Döring, Allen Hicken, Melis Laebens, Staffan I. Lindberg, Juraj Medzihorsky, Anja Neundorf, Ora John Reuter, Saskia Ruth–Lovell, Keith R. Weghorst, Nina Wiesehomeier, Joseph Wright, Nazifa Alizada, Paul Bederke, Lisa Gastaldi, Sandra Grahn, Garry Hindle, Nina Ilchenko, Johannes von Römer, Steven Wilson, Daniel Pemstein, and Brigitte Seim. 2020. "Codebook Varieties of Party Identity and Organisation (V–Party) V1". Varieties of Democracy (V–Dem) Project.

Misc

Project manager(s): Nils Düpont (A01)

Data release: Not yet applicable

Revisions: Not yet applicable

Sources

• Döring, Holger, and Nils Düpont. 2020. "Elections Global: Election results in 207 countries, 1880–2015". Harvard Dataverse, V2. https://doi.org/10.7910/DVN/OGOURC
• Lührmann, Anna, Nils Düpont, Masaaki Higashijima, Yaman B. Kavasoglu, Kyle L. Marquardt, Michael Bernhard, Holger Döring, Allen Hicken, Melis Laebens, Staffan I. Lindberg, Anja Neundorf, Saskia Ruth, Keith R. Weghorst, Nina Wiesehomeier, Joseph Wright, Ora J. Reuter, Nazifa Alizada, Paul Bederke, Lisa Gastaldi, Sandra Grahn, Garry Hindle, Nina Ilchenko, Johannes von Römer, Daniel Pemstein, and Brigitte Seim. 2020. "Varieties of Party Identity and Organization (V-Party) Dataset V1". Göteborg: Varieties of Democracy (V-Dem) Project. https://doi.org/10.23696/vpartydsv1