Under the party-list system, the elector votes not for a single candidate but for a list of candidates. Each list generally is submitted by a different party, though an individual can put forward his own list. District magnitude (i.e., the number of members per district) varies from country to country; for example, the Netherlands uses a single national district to elect the 150 members of its Tweede Kamer (Second Chamber), and Chile elects members of its legislature by using two-seat constituencies.
An open-list system is often incorporated as an additional part of an electoral process, working alongside a constituency system of elections. This ‘mixed’ or ‘additional member’ type of system operates in New Zealand and German legislative elections, and in elections to the Scottish Parliament, Welsh Assembly, and London Assembly.
Most European democracies now use the open list form of party list voting. This approach allows voters to express a preference for particular candidates, not just parties. It is designed to give voters some say over the order of the list and thus which candidates get elected.
In a closed list system--the original form of party list voting--the party fixes the order in which the candidates are listed and elected, and the voter simply casts a vote for the party as a whole. Voters are not able to indicate their preference for any candidates on the list, but must accept the list in the order presented by the party. Winning candidates are selected in the exact order they appear on the original list.
Proportional representation systems prevent the waste of votes in contrast to the United States, we use “winner-take-all” single seat districts, where votes going to a losing candidate are wasted, even if that candidate garners 49.9% of the vote. This leaves significant blocs of voters unrepresented and voters sense this, and so often we do not vote for a candidate we like, but rather the one who realistically stands the best chance of winning—the “lesser of two evils.” Or, all too often, we don’t bother to vote at all.
Some studies argue that strategic voting is also common in proportional representation systems. Their results show that voters’ preferences, rather than mapping directly into party choice, are affected by their expectations on small parties’ re-entry chances.
The mixed-member proportional (MMP) system tries to combine features of party list systems and the first-past-the-post system. Voters cast two votes, one to elect their local member and another to indicate the party they support. The party vote determines what portion of seats each party will have in parliament.
It is the most widely used set of electoral systems in the world, and its variants can be found at some level of government in almost every country (including the United States, where some city councils are elected using forms of PR). The three mostly used forms of proportional representation are: Party list sytems (open and closed-list PR), Single transferable vote (STV) and mixed-member proportional systems.
In proportional representation systems, voters face more complex incentives as electoral outcomes don’t translate as directly into policy outcomes as in plurality rule elections. A common approach is to assume electoral outcomes translate into policy as a vote-weighted average of all party platforms. However, most of the world’s legislatures are majoritarian institutions, and elections in PR systems are generally followed by a process of coalition formation.
Under MMP systems, the PR seats are awarded to compensate for any disproportionality produced by the district seat results. For example, if one party wins 10 per cent of the vote nationally but no district seats, then it will be awarded enough seats from the PR lists to bring its representation up to 10 per cent of the seats in the legislature.