Single member and multi member districts

Original question:

I am currently researching electoral systems and find this website excellent, with lots of useful information; however I am finding some terms a little confusing.  It would be greatly appreciated if you could explain the following terms for me:

• multi-member electoral district

• single member electoral district

Also, if you have any other information about the effectiveness, pros and cons of electoral systems it would be of great help. (eg, pamphlets, booklets, etc).

Links to related resources:

• ACE Encyclopaedia: District Magnitude and Political Parties
  
• ACE Encyclopaedia: Plurality Electoral Systems
  
• ACE Encyclopaedia: Boundary Delimitation

ACE Network Facilitator's response:

Thank you for your question. We are pleased to hear that you find the website useful.

Under the narrow definition of electoral systems – the way in which votes are translated into seats – three elements are particularly salient:

1. The district size (how many representatives are elected in each electoral district; ranges from one to all representatives to be elected to the body in question).
2. The ballot structure (how voters are able to express their choice; one or two ballots, using ticks or numbers, voting for candidates or parties etc.).
3. The formula (how a winner/several winners are chosen; simple plurality, absolute majority, proportional representation etc.).

There are of course many ways of defining and describing electoral systems, but by focussing on these three elements it is possible to distinguish between several types of electoral systems and draw interesting conclusions about political effects of electoral system design.

You asked specifically about the different electoral districts (also known as constituencies):

• A multi-member electoral district (MMD) is an electoral district electing more than one representative to office. All proportional representation systems use MMDs, simply because it is impossible to distribute anything proportionally if there is only one seat. In proportional systems, the simple rule is that the larger the district size the more proportional the system. Other systems using MMDs are Block Vote, Party Block Vote, Mixed Member Proportional systems and Parallel systems.

• A single member electoral district (SMD) is an electoral district electing only one representative to office. The most common electoral system using SMDs is by far the First Past the Post (FPTP) system, under which the one candidate obtaining the most votes in one district is elected, even if he or she has not obtained an absolute majority of the votes. Other electoral systems which most often operate under SMDs are the Alternative Vote (AV) and Two-Round Systems (TRS).

The choice of electoral systems has a significant effect on who is elected, and a great many areas are affected beyond this direct votes to seats relationship. A few of the most prominent ones are:

• Governance
• Representation
• Party formation

As a general rule, plurality/majority systems using SMDs do well when it comes to creating strong majority governments and faithful geographic representation, while proportional representation systems with large MMDs do better when it comes to creating inclusive legislatures and representation of minorities and women.

There is a wealth of literature on electoral systems and their pros and cons. For an introduction to the subject and for a discussion about some of the advantages and disadvantages and criteria that can be considered when designing an electoral system, please see the handbook of electoral system design available in full text on the International IDEA website, and the electoral system topic area in the ACE Encyclopaedia.

Wikipedia also has some interesting articles about different electoral systems.

The opinions expressed by the ACE Network Facilitator do not necessarily reflect those of the ACE Partner organizations.

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