Summary: This entry of about 2250 words defines proportional representation, discusses its different forms, and compares the concept with semiproportional systems.
Proportional representation is a category of electoral systems that translate voter preferences into elected legislative seats. Most commonly used are list formulas that award seats to political parties proportionately based on the number of votes cast per party list. A less commonly used system is the single transferable vote formula in which voters choose specific candidates rather than party lists.
List formulas can be further subdivided into two types: systems based on the highest averages or divisors and those based on the largest remainders or quotas. The main difference between these two is the degree of proportionality, which is also significantly effected by district magnitude and electoral thresholds. The d'Hondt and modified Sainte-Lague are the two most popular highest-average list formulas, although the Hagenback-Bischoff method can provide a useful shortcut when many seats must be allocated. The Hare and Droop quotas are the two most common largest-remainder list formulas, although Italy has adopted its own--the Imperiali quota. The D'Hondt is by far the most popular method used for national legislative elections. The entry provides excellent illustrations of each of these methods for selecting candidates in proportional representation systems.
The entry concludes by considering the merits of proportional representation and single-member district systems. Proportional representative systems allow proportionality and minority representation while single-member district systems emphasize two-party pressures and close voter-representative contact. Semiproportional or semiplurality systems (cumulative vote, limited vote and single nontransferable vote) are intermediate systems that combine the beneficial attributes of pure proportional and single-member systems.