Majority bonus

The majority bonus system (MBS) is a form of semi-proportional representation used in some European countries. Its feature is a majority bonus which gives extra seats or representation in an elected body to the party or to the joined parties with the most votes with the aim of providing government stability.

It is used in Greece, Italy and San Marino.

Benito Mussolini was the first politician to enact a law to give automatic seats to the winning party and ensured his victory in the Italian election of 1924. The majority bonus system was used again after the restoration of the democracy but within basic limits, awarding a number of seats to allow government stability but not large enough to allow a single party to promulgate constitutional changes. It was used in Italian local elections in the 1950s and was reintroduced for local elections in 1993 and national ones in 2005 to replace the additional member system. After a 2013 ruling from the Constitutional Court stating that unlimited bonuses are unconstitutional, a 40% minimum threshold for the assignment of the bonus has been established, with a runoff ballot between the two most voted parties if the threshold is not reached.

The MBS was adopted by other European countries, especially Greece in 2004 and San Marino at the national level, and France for its regional elections.

It can be based on any form of mechanism used in party-list proportional representation, but a D'Hondt method is most likely, as it will rank seats in an exact order of vote share.

Basically, there are two different forms of majority bonus systems, with clearly different political results:

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