How does district magnitude affect the proportionality of an election result?

In the context of proportional representation, district magnitude is the single most significant factor influencing the proportionality of election results. District magnitude refers to the number of legislative seats assigned to an individual constituency.1

The relationship between district magnitude and proportionality is direct: as the number of seats per electoral district increases, the election outcome becomes more proportional to the distribution of the popular vote. Conversely, smaller district magnitudes tend to result in less proportional outcomes, as they make it more difficult for smaller parties to secure representation. By utilizing multimember constituencies, proportional systems aim to reflect the diverse opinions within the electorate more accurately than plurality or majority systems, though perfect proportionality is rarely achieved in practice.1