Defined as “the degree of disproportionality produced between the shares of votes and the shares of seats gained by each competing party”, electoral disproportionality is calculated on the basis of the following formula:
LSq. = [0.5(Σ|vi-si|)²]½
In which vi and si respectively represent the proportion of votes and seats of the ith party (see Gallagher, 1991; Casal Bértoa, 2013: 403-406, 428).
Please cite the following database as: Casal Bértoa, F. (2016): Database on WHO GOVERNS in Europe and beyond, PSGo. Available at: whogoverns.eu