Overhang seat

Overhang seats are constituency seats won in an election under the traditional mixed member proportional (MMP) system (as it originated in Germany), when a party's share of the nationwide votes would entitle it to fewer seats than the number of individual constituencies won. The electoral reform in Germany removed the overhang seats, and replaced with Zweitstimmendeckung. Under MMP, a party is entitled to a number of seats based on its share of the total vote. If a party's share entitles it to ten seats and its candidates win seven constituencies, it will be awarded three list seats, bringing it up to its required number. This only works, however, if the party's seat entitlement is not less than the number of constituencies it has won. If, for example, a party is entitled to five seats, but wins six constituencies, the sixth constituency seat is referred to as an overhang seat. Overhang can result from an unproportional distribution of constituencies as well as strong region-based support or the existence of regional parties. The two mechanisms that together increase the number of overhang seats are: winning many constituencies; decreasing the number of party votes and therefore the number of seats to which the party is proportionally entitled. In many countries, overhang seats are rare – a party that is able to win constituency seats is generally able to win a significant portion of the party vote as well. There are, however, some circumstances in which overhang seats may arise relatively easily: Few major parties, large number of minor parties – When there are only one or two major parties, but a relatively large number of minor parties that, combined, achieve a significant share of the total proportional vote, but fail to elect any constituency seats, the large parties often end up with overhang seats. Similar lead across constituencies – If one party wins all or most constituencies of a relevant area with a rather low margin, it would be more prone to overhang mandates than if different parties lead in different constituencies, with the same overall share of each of the parties.