Why can proportional representation lead to more political parties in a legislature?

Proportional representation leads to a larger number of political parties in a legislature because it is designed to ensure that the distribution of legislative seats broadly reflects the distribution of the popular vote. Unlike plurality or majority systems, which often reward large parties and penalize smaller ones by awarding an entire constituency's representation to a single candidate, proportional representation allows smaller parties to secure seats even without winning a majority or plurality of the vote.123

By using multimember constituencies, these systems provide a path for diverse political groups to gain representation proportionate to their electoral support. Because the system does not inherently favor large parties over smaller ones, it effectively encourages the presence of three or more parties in the legislature, which typically necessitates the formation of coalition governments to manage policy. While factors such as district magnitude and specific electoral formulas influence the degree of proportionality, the fundamental mechanism of the system is to translate a census of public opinion into legislative presence, thereby fostering a multiparty environment.1234