More seats, more parties. For assembly and parliamentary elections, the larger the size of the assembly and the higher the district magnitude with proportional representation, the higher the number of political parties.
Micro–mega rule. Large parties prefer small assemblies and small district magnitudes by plurality rule, while small parties prefer large assemblies and large districts with proportional representation.
Small assemblies, large districts. The development of multiple parties favors the adoption of large multi–seat districts with proportional representation rules. In the long term, proportional representation rules have been increasingly adopted. But in very large countries, a large federal assembly can be elected with different electoral rules, including small single–seat districts