Phragmen Rules for Degressive and Regressive Proportionality

Speaker(s)

Michał Jaworski

Affiliation

Uniwersytet Warszawski

Date

May 12, 2022, 10:15 a.m.

Room

room 4050

Seminar

Seminar Games, Mechanisms, and Social Networks

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We study two concepts of proportionality in the model of approval-based committee elections. In degressive proportionality small minorities of voters are favored in comparison with the standard linear proportionality. Regressive proportionality, on the other hand, requires that larger subdivisions of voters are privileged. We introduce a new family of rules that broadly generalize Phragmén's Sequential Rule spanning the spectrum between degressive and regressive proportionality. We analyze and compare the two principles of proportionality assuming the voters and the candidates can be represented as points in an Euclidean issue space.

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