Why do larger electoral districts usually produce more proportional results?

In the context of proportional representation, the term "district magnitude" refers to the number of legislative seats assigned to a single electoral district. This is the most significant factor in determining how closely an election outcome reflects the actual distribution of the popular vote.1

Larger electoral districts—those that elect a higher number of representatives—usually produce more proportional results because they lower the threshold of votes required for a party to win a seat. In a district with only a few seats, a party must secure a relatively large percentage of the vote to gain representation. As the number of seats per district increases, the system becomes more inclusive, allowing smaller parties or diverse political groups to win seats that would be unattainable in smaller or single-member constituencies.1

By facilitating the representation of a wider array of political opinions, larger districts help ensure that the legislative body more accurately mirrors the electorate's overall preferences, thereby reducing the disproportionality often found in majority or plurality systems.1