An election apportionment diagram is the graphic representation of election results and the seats in a plenary or legislative body. The chart can also be used to represent data in easy to understand terms, for example by grouping allied parties together.

Votes in an election are often represented using bar charts or pie charts, often labeled with the corresponding percentage or number of votes.^[1] The apportionment of seats between the parties in a legislative body has a defined set of rules, unique to each body. As an example, the Senate of Virginia says,

The Clerk of the Senate, after the election of Senators, shall assign desks to the individual Senators with the Senators elected as members of the majority party in the Senate in the chamber area beginning at the north side of the chamber until all such desks have been assigned, and then the Senators elected as members of the minority party in the Senate, and then any Senator not elected as a member of the two major political parties.^[2]

Instead of using a bar or pie chart, the apportionment of seats between the parties in a legislative body such as a parliament can be represented more clearly by displaying the individual representatives of each party as dots in a pattern, because the number of representatives is also significant, and is easily understood visually. The dots are typically coded according to the political color of the respective parties.^[3] This was traditionally presented as a seating chart of a plenary hall, but can also be represented in a more abstract fashion which more loosely corresponds to the seating arrangement in a legislature, for example a form of half-donut chart as an abstract representation of a hemicycle, or a stylized representation of the Westminster Parliament, showing government, opposition, speaker and crossbenchers. In Germany, the order of the bars usually corresponds from left to right to the placement of the parties in the previous election and is thus based on the order given on the ballot, which is regulated in Section 30 of the Federal Electoral Act [de].^[4]

These charts can also be used to represent data in easy to understand terms.^[5] An example of this is politicians’ responses to the Orlando shootings.^[6]

• Schematic diagram of the House of Lords, showing government, opposition, cross-bench and speaker, without being an accurate representation of the seating layout
• Stylised U-shaped diagram meant to depict the layout of the Northern Ireland Assembly
• An election apportionment diagram closely mirroring the actual seating layout of the Bundestag

• Red states and blue states