One factor that can influence the implementation of voluntary party quotas is the electoral system. Proportional representation systems in particular are claimed to facilitate the election of a diverse pool of representatives.

In single-member constituencies (which are common in majority/plurality electoral systems), each party organisation can generally nominate only one candidate. In practice, parties tend to select the candidate to whom they attribute the greatest chances of winning: in practice, this is often a man and often a member of the majority group. This makes it more difficult to implement voluntary quotas, and women and members of minority groups are often nominated only in constituencies where the party does not see any chance of winning. Therefore, quotas in majority/plurality systems tend to produce fewer elected women and minority candidates  than quotas in proportional systems.[1]

Political parties compete for a larger number of seats per constituency in a proportional representation system and can therefore “balance the party ticket” between competing factions inside the party (ibid). Otherwise disadvantaged party members often benefit from this balancing process. Given that the seats in proportional representation systems are allocated to the party in proportion to their share of the national vote, the party can also, under some PR systems, decide over the rank ordering of the candidates. Certain candidates can be placed in more promising party list positions than others. This makes voluntary party quotas work better in proportional representation systems where a share of the candidacies can be allocated to under-represented groups. To make voluntary party quotas even more effective, political parties often have a placement criteria (also called “double quota”) that ensures that persons who take advantage of the quota are not only placed on the candidate list, but placed in winnable positions – i.e., in positions the party expects to win. If a party expects to win five seats in a fifteen-seat constituency, positions one through five on the party’s candidate list are “winnable” while positions six through fifteen are not.

Another important factor for the implementation of voluntary party quotas is the political culture in the country. If greater representation is encouraged by the political elite, media, and ultimately the voters, political parties are more likely to see the advantages of voluntary party quotas. The openness of a political culture determines the opportunities underprivileged social group members have to gain influence over political decisions.

Party culture has an impact on the implementation of quotas. Positive discrimination in favour of underprivileged groups by quota systems is said to be more consistent with certain political parties than with others, for instance with Labour or welfare state parties. Their party culture or main policy of intervention and redistribution to combat social or economic inequalities is very similar to the intervention by a quota system and its allocation rules.