Description
Decomposition of Seats-to-Votes Distortion in Multimember Elections.
Description
Decomposes the seat-to-vote distortion for every party (individual party bias or individual party deviation from proportional representation) into segments that can be attributed to separate causes for the party infra or over-representation: the electoral system effect (separating the mean and the variance effect within it) and the population effect (separating malapportionment and unequal participation effect within it). It works on (single tired) districted electoral systems with any number of seats per district. In addition, the package aggregates the individual party distortion into an index of deviation from proportionality (the Losemore-Hanby index) whose value is also decomposed into segments attributed to the major causes of deviation from proportionality (plus the interactions among them).