Simple-majority rule and the size of the Bundestag

How should an excessively large parliament be effectively reduced in size without violating constitutional principles? This is a question that the German Bundestag discussed since introducing the 2013 electoral reform until today. Facing a Bundestag consisting of 709 members and facing some public dissatisfaction, are reform to decrease the parliament’s size was adopted in 2020. With the 2017 elections taking place under the new electoral rule, the size would have been 686 instead of 709. However, the opposition filed a lawsuit against the new electoral law with the German Federal Constitutional Court. Aside from legal considerations, the adherence to plurality rule has to be criticised from a social-choice perspective. This paper aims to determine if the size and composition of the Bundestag change. Inparticular, whether the size is reduced when the German parliament’s directly-elected members are elected using the simple-majority rule. Thus, a statistical simulation is carried out. We show that the targeted size of the Bundestag of 686 MP can be achieved by using the simple-majority rule to select the directly-elected members of parliament. Though, as we find indications that even Condorcet losers were elected into parliament, applying the simple-majority rule would ensure that only Condorcet winner would be elected directly into the Bundestag.