Proportional representation

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Proportional representation (PR) refers to any type of electoral system under which subgroups of an electorate are reflected proportionately in the elected body.^[1] The concept applies mainly to political divisions (political parties) among voters. The essence of such systems is that all votes cast – or almost all votes cast – contribute to the result and are effectively used to help elect someone. Under other election systems, a bare plurality or a scant majority are all that are used to elect candidates. PR systems provide balanced representation to different factions, reflecting how votes are cast.

Proportional representation means that each representative in an assembly is elected by a roughly equal number of voters. In the common case of electoral systems that only allow a choice of parties, the seats are allocated to parties in proportion to the vote tally or vote share each party receives.

Due to various factors, perfect proportionality is rarely achieved under PR systems. Optional rules applied in some PR systems may affect proportionality. Sometimes that effect is intended such as to suppress representation of small, extreme parties. The use of electoral thresholds (in list PR or MMP), small districts with few seats in each (in STV or list PR), or the absence or insufficient number of leveling seats (in list PR, MMP or AMS) may produce disproportionality. Other sources of disproportionality are electoral tactics, such as party splitting in some MMP systems.

Nonetheless, PR systems approximate proportionality much better than other systems^[2] and are more resistant to gerrymandering and other forms of manipulation.