Proportional representation voting (PR) is the main rival to plurality-majority voting. Among advanced western democracies it has become the predominant voting system. For instance, in Western Europe, 21 of 28 countries use proportional representation, including Austria, Belgium, Cyprus, Denmark, Finland, Germany, Greece, Ireland, Luxembourg, Malta, the Netherlands, Norway, Portugal, Spain, Sweden, and Switzerland.
The basic approach of proportional representation is simple: legislators are elected in multimember districts instead of single-member districts, and the number of seats that a party wins in an election is proportional to the amount of its support among voters. So if you have a 10-member district and the Republicans win 50% of the vote, they receive five of the ten seats. If the Democrats win 30% of the vote, they get three seats; and if a third party gets 20% of the vote, they win two seats. Electoral system designers have devised several ways to achieve these proportional results, and so there are three basic kinds of PR described below: party list, mixed-member, and single-transferable vote (also called choice voting).