Working Paper

Economia Política

Amedeo Piolatto

2009/27: Plurality versus proportional electoral rule: which is most representative of voters?

This study compares the representativeness of voters in the proportional electoral system with the situation under plurality rule. Representativeness is commonly measured by comparing parties’ received votes with their shares of seats in the Parliament; this implies that proportional rule should always better represent voters. A coalition within the Parliament, however, rules the country without interference and supports the government; when a coalition is formed, the pivotal role of small parties and the proposal right of the formateur can significantly impact the distribution of power. Focusing on the coalition formation stage, I demonstrate that the proportional rule is more representative only under very specific conditions. If these conditions are not met, introducing some distortions in the distribution of seats among parties can actually improve representativeness.