How did proportional representation work in Weimar Republic elections?

The Weimar Republic (1918–1933) utilized a system of proportional representation for Reichstag elections, which allowed for a high degree of democratic representation but is often cited by historians as a contributing factor to the republic's political instability.12

Under this system, political parties received seats in the legislature in direct proportion to the share of the total vote they secured. Unlike systems that use single-member districts, this approach encouraged the proliferation of numerous political parties, as smaller groups could more easily gain representation.32

While this ensured that the legislature reflected a wide diversity of public opinion, it also led to significant political fragmentation. Because no single party could easily command a majority, the government was forced to rely on coalition building. This environment made it difficult to maintain stable cabinets, as the withdrawal of support from coalition partners could cause the government to collapse. Furthermore, because the Weimar system lacked the electoral thresholds (such as the 5 percent rule used in modern Germany) that help exclude extremist or splinter parties, radical groups from both the left and the right were able to gain parliamentary seats, which they sometimes used to undermine the constitutional order.241