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How do we start thinking about elections? At one level they are deceptively simple: Politicians compete for public support. Voters respond on election day by indicating who they prefer. The votes are tallied and translated into seats in the Legislature. And the electoral system organises shapes and governs the process.
 WHAT IS AN ELECTORAL SYSTEM?
An electoral or voting system is how votes are translated into seats. It determines how many votes and what kinds of votes are necessary to award seats to candidates and parties in an election. Different electoral systems produce different kinds of results, and give voters different kinds of choices.
The electoral system determines the “exchange rate” between votes and seats - that is, how votes are translated into seats. How many and what kind of votes are needed to get a seat varies from system to system. As a result, different electoral systems give politicians incentives to organize and campaign in different ways. Some electoral systems may even create barriers for certain types of candidates. Different electoral systems give voters different kinds of choices, which can then affect the decisions voters make.
WHAT TYPES OF ELECTORAL SYSTEMS EXIST?
There are three main types or families of electoral systems in the world, with several variations among each one. The three main types are:
- Plurality – candidates are elected with a plurality (i.e. not a majority) of votes cast. Main models include: Single Member Plurality; Multi-Member Plurality (also called Block Vote).
- Majority – candidates are elected with a majority (i.e. more than 50%) of votes cast.
- Main models include: Alternative Vote; Two-Round Vote.
- Proportional Representation – candidates are elected based on the total percentage of votes cast for their party. Main models include: List; Mixed Member Proportional; Single Transferable Vote; Single Non-Transferable Vote; Parallel.
|
Electoral
system |
Districts
|
Type
|
Description
|
|
first-past-the-post
(FPTP) |
single-member |
plurality |
The
candidate that obtains more votes than any other is
elected, even if that person only won a minority of
votes cast |
|
two-round
system (TRS) |
single-member |
majority |
A
runoff election is held between the two top vote-getters,
in order to ensure that the winner obtains a majority
of votes cast |
|
alternative
vote (AV), or instant runoff |
single-member |
majority |
Voters
indicate an order of preference among candidates. If
no candidate obtains a majority outright, the last-place
candidate is removed, and the associated second-choice
votes are added to the totals of the remaining candidates.
The process is repeated until a candidate secures a
majority. |
|
block
vote (BV) |
multiple-member |
plurality |
Voters
may cast as many votes as there are open seats. If there
are n seats to be filled, the top n vote-getters are
elected |
|
single
non-transferable vote (SNTV) |
multiple-member |
semi-proportional |
Voters
can only cast a single vote among candidates for n seats.
The top n vote-getters are elected. |
|
single
transferable vote (STV), also known as preference or
choice voting |
multiple-member |
proportional |
Voters
indicate an order of preference among candidates. Candidates
whose first-choice vote totals attain the Hare Quota—(votes
cast/n+1) + 1— are elected. The last-place candidate
is removed, and the associated second-choice votes are
added to the totals of the remaining candidates. The
process is repeated until all n seats are filled. |
|
mixed
member proportional (MMP) |
mixed |
proportional |
The
legislature consists of a block of seats that are elected
by plurality or majority from single-member districts,
and another block of seats that are elected in multi-member
districts under a proportional system. The proportional
seats are awarded in such a way as to compensate for
disproportional effects in the single-member district
outcomes. |
|
parallel |
mixed |
semi-proportional |
The
legislature consists of a block of seats that are elected
by plurality or majority from single-member districts,
and another block of seats that are elected in multi-member
districts under a proportional system. The proportional
seats are awarded independently of the outcomes in single-member
districts. |
|
party
list |
multiple-member |
proportional |
Voters
choose from among party lists, and seats are awarded
in proportion to the vote received by each party. Candidates
are seated in the order listed. |
source:
http://worldpolicy.org/globalrights/democracy/types.html |
