Mixed Electoral Systems

The Best of Both Worlds?

Mixed electoral systems attempt to combine the advantages of majoritarian and proportional systems. The basic idea is that some members are elected from single-member districts (providing local representation) while others are elected from party lists (providing proportionality). The key question is how these two components interact.

There are two main types. Mixed-member proportional (MMP) systems, used in Germany and New Zealand, use the proportional component to compensate for disproportionality in the district results. If a party wins fewer district seats than its vote share warrants, it receives additional list seats to make up the difference. Mixed-member majoritarian (MMM) systems, used in Japan and South Korea, keep the two components separate: district results stand on their own, and list seats are allocated independently.

Germany's MMP System

Germany's Bundestag uses MMP with a two-vote system. Each voter casts a first vote (Erststimme) for a district candidate and a second vote (Zweitstimme) for a party list. The 299 district seats are awarded to the plurality winner in each district. Then, list seats are allocated so that each party's total seats (district plus list) match its share of the second vote, subject to a 5 percent threshold.

This design has produced stable coalition governments while maintaining high proportionality. However, the system has grown more complex over time. 'Overhang seats' (Ueberhangmandate) arise when a party wins more district seats than its vote share would warrant, and 'leveling seats' (Ausgleichsmandate) are added to restore proportionality for other parties. These additions have caused the Bundestag to balloon from its target of 598 seats to over 700 in recent elections, prompting a major reform passed in 2023 that caps the chamber's size.

MMP vs MMM at a Glance

A worked example makes the difference concrete. Picture a 200-seat legislature (100 districts, 100 list seats) where a party wins 30 percent of the list vote and 40 of the 100 districts. Under MMP, its target is 30 percent of 200 = 60 seats, so it receives only 20 list seats to top up its 40 districts — a proportional result. Under MMM, the district wins simply stand, and it also collects 30 percent of the 100 list seats = 30 more, for 70 seats total. The same votes yield an overrepresented party under MMM because its district victories are never offset.