Cancellation of overhang seats: the price of unkept promises

Abstract Mixed Member Proportional (MMP) electoral systems aim to balance territorial representation, personal voter-politician connections, and party proportionality. However, legislators face significant challenges in achieving these goals simultaneously. In Germany, these efforts led to the pressing issue of overhang seats, which prompted a reform of the electoral system in 2023. This study examines the effects of this reform and three alternative solutions discarded during the legislative process, focusing on their impact on representation and proportionality. We evaluate these solutions using various inequality indexes and their specific components to address issues such as disproportionality, malapportionment, and wasted votes. Our analysis includes counterfactual recalculations of the 2025 Bundestag election results across four alternative electoral systems: the German electoral system first used in the 2025 elections, the German electoral system used until 2021 elections, and two systems using the restricted Sainte-Laguë/Webster method to allocate votes, with or without inviolability of direct mandates. Our findings reveal minimal differences in unequal representation among the systems. However, the adopted solution introduces the controversial phenomenon of “orphaned seats” disproportionately affecting major political forces like the CDU/CSU and AfD. This fact is particularly significant in the specific context of German politics, but it reveals a certain vulnerability in the reform — it is difficult to expect stability from a solution whose most controversial effect is felt most acutely by the strongest players.