##  [Effective Number of Parties](/index.php/effective-number-parties) 

  ##  [Effective Number of Parties](https://social.quantumdictionary.io/effective-number-parties-0) 

  

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**Social Sciences Dictionary**

 







 

 

 

 



 

 

 

 

Definition

A numerical index summarizing party-system fragmentation by weighting each party according to its vote or seat share; commonly computed as ENP = 1 / Σ s_i^2, where s_i are party shares expressed as fractions of the relevant total.