All other things being equal, the electoral systems not only affect the process of converting obtained votes to parliamentary seats (mechanical effect) but also the incentive structure of voters and politicians (psychological-strategic effect). From this political effect of electoral systems, this paper infers that politicians and parties would prefer an electoral system that favorably converts support for them into parliamentary seats, and further seek for the change to such electoral system if they are allowed to do it.
For example, those who come into power without the voluntary support of voters (e.g. military coup d'etat) will pursue changes in electoral system so as to disrupt the voters' support structure toward the existing party system. In addition, change of electoral system will be sought when electoral environment comes to be disadvantageous due to decrease in voters' support to those in power, despite their efforts to stay in power. To find evidences that prove these inferences, this paper analyzes changes of the electoral systems for the Korean National Assembly.
Furthermore, this paper asserts that the fairness of the adopted system differs depending on the amending process. When the amending process is monopolized by a certain group, an unfair electoral system that benefits the group tends to be adopted. However, when several groups participate in the amending process, there tends to be a high possibility of adopting a relatively fair electoral system.