Plurality versus proportional electoral rule: study of voters' representativeness

Thinking of electoral rules, common wisdom suggests that proportional rule is more fair, since all voters are equally represented: at times, it turns out that this is false. I study the formation of both Parliament and Government; for the composition of the former I consider plurality and proportional rule; for the formation of the latter, I assume that parties play a non-cooperative game à la Rubinstein. I show that, unless parties are impatient to form a Government, proportional electoral rules translate into a more distortive distribution of power among parties than plurality rule; this happens because of the bargaining power of small parties during Government formation.