Tideman's Alternative Methods, including Alternative Smith and Alternative Schwartz, are two
electoral systems developed by
Nicolaus Tideman
Thorwald Nicolaus Tideman (, not ; born August 11, 1943 in Chicago, Illinois) is a Georgist economist and professor at Virginia Tech. He received his Bachelor of Arts in economics and mathematics from Reed College in 1965 and his PhD in economics ...
which select a single winner using votes that express
preferences
In psychology, economics and philosophy, preference is a technical term usually used in relation to choosing between alternatives. For example, someone prefers A over B if they would rather choose A than B. Preferences are central to decision the ...
. These methods can also create a sorted list of winners.
These methods are
Smith
Smith may refer to:
People
* Metalsmith, or simply smith, a craftsman fashioning tools or works of art out of various metals
* Smith (given name)
* Smith (surname), a family name originating in England, Scotland and Ireland
** List of people wi ...
- and
Schwartz-efficient, respectively, and thus are
Condorcet method
A Condorcet method (; ) is an election method that elects the candidate who wins a majority of the vote in every head-to-head election against each of the other candidates, that is, a candidate preferred by more voters than any others, whenever ...
s. They operate by using
instant-runoff voting
Instant-runoff voting (IRV) is a type of ranked preferential voting method. It uses a majority voting rule in single-winner elections where there are more than two candidates. It is commonly referred to as ranked-choice voting (RCV) in the Un ...
for
cycle resolution.
Procedure
![Tideman-Alternative-Smith](https://upload.wikimedia.org/wikipedia/commons/2/25/Tideman-Alternative-Smith.png)
Tideman's Alternative procedure is as follows:
# Identify the Smith or Schwartz set.
# If the set consists of
one candidate, elect that candidate.
# Eliminate all candidates outside the set and redistribute ballots.
#
Eliminate the plurality loser.
# Repeat the procedure.
To create a sorted list of preferred candidates, select a winner, remove that winner from the list of candidates, and repeat.
Features
Tideman's Alternative Methods are easier to understand than other methods, such as
Ranked Pairs
Ranked pairs (sometimes abbreviated "RP") or the Tideman method is an electoral system developed in 1987 by Nicolaus Tideman that selects a single winner using votes that express preferences. The ranked-pairs procedure can also be used to create ...
and
Schulze
Schulze is a German surname, from the medieval office of Schulze, or village official. Notable people with the surname include:
* Andrew Schulze (1896–1982), clergyman and civil rights activist
* William August Schulze, rocket scientist recru ...
, owing to the simplicity of explaining both the
Smith set
In voting systems, the Smith set, named after John H. Smith, but also known as the top cycle, or as Generalized Top-Choice Assumption (GETCHA), is the smallest non-empty set of candidates in a particular election such that each member defeats ever ...
(the smallest set of all candidates who each defeat every non-Smith candidate) and
Instant run-off voting
Instant-runoff voting (IRV) is a type of ranked preferential voting method. It uses a majority voting rule in single-winner elections where there are more than two candidates. It is commonly referred to as ranked-choice voting (RCV) in the Un ...
(eliminating the candidate with the fewest votes). This increases the likelihood of voter acceptance.
This method strongly resists both tactical voting and tactical nomination, reducing the amount of political manipulation possible or favorable in large elections. They inherit this resistance from
instant run-off voting
Instant-runoff voting (IRV) is a type of ranked preferential voting method. It uses a majority voting rule in single-winner elections where there are more than two candidates. It is commonly referred to as ranked-choice voting (RCV) in the Un ...
, as both methods resolve a Condorcet winner from the Smith set by eliminating non-Smith (or non-Schwartz) candidates and performing instant run-off voting on the result.
Although IRV itself faces criticism for theoretical and
historical failures, all Smith- and Schwartz-efficient voting methods attempt to resolve a candidate from these respective sets. Unlike IRV, these methods invariably elect a Condorcet winner; when there is none, they elect different winners based on arbitrary criteria.
Ranked Pairs
Ranked pairs (sometimes abbreviated "RP") or the Tideman method is an electoral system developed in 1987 by Nicolaus Tideman that selects a single winner using votes that express preferences. The ranked-pairs procedure can also be used to create ...
elects the winner with the strongest overall ranking, while the
Schulze method
The Schulze method () is an electoral system developed in 1997 by Markus Schulze that selects a single winner using votes that express preferences. The method can also be used to create a sorted list of winners. The Schulze method is also known a ...
attempts to elect a winner without the worst pairwise loss. Tideman's Alternative Method elects a candidate in a manner strongly resisting tactical nomination and voting.
Tideman's Alternative Methods fail
independence of irrelevant alternatives
The independence of irrelevant alternatives (IIA), also known as binary independence or the independence axiom, is an axiom of decision theory and various social sciences. The term is used in different connotation in several contexts. Although it ...
. However, the methods adhere to a less strict property, sometimes called
independence of Smith-dominated alternatives
Independence of Smith-dominated alternatives (ISDA, also known as Smith- IIA or Weak independence of irrelevant alternatives) is a voting system criterion defined such that its satisfaction by a voting system occurs when the selection of the win ...
(ISDA). It says that if one candidate (X) wins an election, and a new alternative (Y) is added, X will win the election if Y is not in the
Smith set
In voting systems, the Smith set, named after John H. Smith, but also known as the top cycle, or as Generalized Top-Choice Assumption (GETCHA), is the smallest non-empty set of candidates in a particular election such that each member defeats ever ...
. ISDA implies the Smith criterion and Condorcet criterion.
Note that the Condorcet winner can be used as the "set" (if there is a Condorcet winner, they are the only member of the set. Otherwise, all candidates are in the set). This variation is known as Benham's method.
Comparison table
The following table compares Tideman's Alternative Methods with other
preferential single-winner election methods:
References
* Green-Armytage, James
Four Condorcet-Hare Hybrid Methods for Single-Winner Elections
{{voting systems
Non-monotonic Condorcet methods
Single-winner electoral systems