Measuring Representativeness in Different Electoral Systems, Using Italian and Dutch Data

I use power indices to assess the level of representative efficiency of different electoral systems. A representative democracy should “give voice” to as many people’s preferences as possible. This paper evaluates how close a given electoral system is to mirroring the distribution of votes cast in an election. To this goal, both power indices and differences between shares of votes received and seats gained are used. The distribution of power is also compared with both the share of seats of parties in the assembly and the share of votes obtained in the election. The results show that proportional systems and run-off majority are more efficient in terms of representativeness than first-past-the-post methods. Moreover, as the total number of seats in a parliament decreases, representative efficiency tends to increase. The analysis is conducted through simulations using conditional and real (Dutch and Italian) data.