Coalition voting (Q1200885)

Coalition voting is a voting procedure for electing a parliament and choosing a governing coalition under a system of proportional representation of parties. Voters cast two different kinds of votes. First, a party vote where each individual can vote for more than one party. The party vote being evenly divided (for instance, if a voter votes for three parties, each party receives a 1/3 vote). Second, a coalition vote for all coalitions of parties that are ``acceptable'' because they include all parties that the voter designates \(Y\) (``yes'') and exclude all parties designated \(N\) (``no''). The majority coalition acceptable to most voters and that has no superfluous parties becomes governing, provided that the parties it comprises agree. Theoretical properties of coalition voting are analysed. It is shown, in particular, that it is not always rational to vote sincerely. The three- party case is thoroughly investigated. Possible uses for Israel and Italy are discussed.