The plurality electoral system is the oldest and the most frequently used voting system. It is used for legislative elections in the United States and India--the world's two largest liberal democracies--as well as the United Kingdom and many former British colonies. Most of these countries also employ single-member districts, which must be redrawn periodically to remain relatively equal in population.
Proponents of plurality electoral systems cite three main advantages--simplicity, stability, and constituency representation. The plurality system is easy to understand; voters simply place a mark next to their preferred candidate. The result of an election under the plurality system is also easy to understand; the candidate receiving the highest number of votes wins. This allocation rule is referred to as 'first past the post.'
Because of their tendency to produce a disproportionately large number of seats for the majority party, plurality systems usually produce strong single-party governments. This, in turn, produces a stable political system because there is no need to form coalition governments.
Plurality Systems and Single-Member Districts
Plurality electoral systems are most commonly associated with single-member districts and 'first past the post' allocation rules. The use of single-member districts creates a strong link between representatives and their constituencies. Because each representative is beholden to a specific geographically defined constituency, legislative accountability and constituency services are both facilitated. For more information on plurality 'first past the post' systems (see First Past the Post (FPTP)).
Plurality Systems and Multimember Districts
A few plurality systems use multimember districts and different rules for allocating seats in the legislature. The allocation rules for multimember districts under plurality systems include the following:
Block Vote. This voting system gives each elector as many votes as there are seats to be filled. The winners of an election are the candidates receiving the highest numbers of votes. Because the block vote allows the party with the majority of the votes to win all of the seats in a district, the use of the block vote system frequently results in an even greater distortion of seats to votes than does 'first past the post' voting in single-member districts. For more information on the block vote, see Block Vote.
Limited Vote. Under this voting scheme, each elector is given fewer votes than the number of seats to be filled. The expectation under the limited vote is that the majority party will not be able to carry all of the seats in an electoral district if the minority party presents a limited number of candidates and minority party supporters concentrate their votes on those candidates. This voting scheme is used in Spain to elect the upper house of the national parliament. For more information on the limited vote, see Limited Vote.
Single Non-Transferable Vote. This voting system is a variant of the limited vote--each elector is given only one vote. The single non-transferable vote was used in Japan to elect the lower house of the national parliament until 1994. It is still used in Japan to elect 152 of the 252 members of the upper house. For more information on the single non-transferable vote, see Single Non-Transferable Vote.
Conclusion
The process of electoral district delimitation in a plurality system is important because the configuration of districts can affect the partisan, and possibly even the racial, ethnic, religious or linguistic composition of the legislature. The effect may be intentional, as in a partisan 'gerrymander,' or it may be unintentional. Even district boundaries drawn by a neutral boundary commission may unintentionally favour one party over others.
