Most countries with proportional representation systems do not delimit electoral districts. However, two countries that use the single transferable vote, namely Ireland and Malta, do periodically delimit electoral districts2.
Districts are redrawn in Ireland and Malta because the single transferable vote operates best with uniformly small multimember constituencies. Votes are cast by ranking candidates in order of preference, and if there are a large number of seats to fill, the number of candidates on the ballot may be overwhelming. Malta employs only five-member electoral districts. In Ireland, electoral districts range in magnitude from three to five members.
Under a proportional system using the single transferable vote, electors rank candidates in order of preference. If a candidate has so many votes that an elector's first preference is not needed, or if the candidate has so few votes that there is no chance he or she can win office, the elector's first preference is transferred to a second or subsequent choice. To be elected, a candidate must obtain a quota of the votes. The quota is computed simply by dividing the total number of votes cast by one more than the number of seats to be filled, plus one additional vote. Only the prescribed number of candidates to be elected can reach the quota. For more information about the single transferable vote, see Single Transferable Vote.
The single transferable vote system differs from majority and plurality electoral systems in that election outcomes are more proportional. The single transferable vote shares two features in common with majority and plurality systems. Voters choose among candidates, rather than between political parties; and the country is divided into relatively small territorial constituencies. These electoral constituencies, or districts, must be redrawn on occasion to accommodate shifts in the population. For example, in Ireland the constitution stipulates that constituencies be revised at least once every twelve years. Prior to 1980 and the establishment of an independent electoral commission, boundary changes and the allocations of seats in the legislature in Ireland were thought likely to benefit the political party in power.
