In its most simple form, List PR involves each party presenting a list of candidates to the electorate in each multi-member electoral district. Voters vote for a party, and parties receive seats in proportion to their overall share of the vote in the electoral district. Winning candidates are taken from the lists in order of their position on the lists.
The choice of List PR does not in itself completely specify the electoral system: more details must be determined. The system used to calculate the allocation of seats after the votes have been counted can be either a Highest Average or a Largest Remainder Method. The formula chosen has a small but sometimes critical effect on the outcomes of elections under PR. In Cambodia in 1998, a change in the formula a few weeks before polling day turned out to have the effect of giving the largest party 64 seats, instead of 59, in a 121-seat National Assembly. The change had not been well publicized, and it was with difficulty that the opposition accepted the results. This example clearly demonstrates the importance for electoral system designers of apparently minor details.
Cambodian closed List PR ballot paper
There are several other important issues that need to be considered in defining precisely how a List PR system will work. A formal threshold may be required for representation in the legislature: a high threshold (for example 10 per cent, as used by Turkey) is likely to exclude smaller parties, while a low threshold (for example 2 per cent, as used by Israel) may promote their representation. In South Africa, there is no formal threshold, and in 2004 the African Christian Democratic Party won six seats out of 400 with only 1.6 per cent of the national vote. List PR systems also differ depending on whether and how the voter can choose between candidates as well as parties, that is, whether lists are closed, open or free (panachage). This choice has implications for the complexity of the ballot paper.
Other choices include arrangements for formal or informal ‘vote pooling’; the scope for agreements between parties, such as that provided by systems which use apparentement; and the definition of district boundaries.
