While the "Compromise" examples suggest a block of voters could (for
whatever reason) rank a second or third preference higher than their
actual first preference, the tactic is effective only if these voters
have already given up on their first preference (essentially making the
second choice the NEW first choice). It is no different than Nader
supporters sensing a losing battle and choosing to cast their non-IRV
votes for Gore (or whomever).
There is no discernible advantage, however, to listing a preferred
candidate "lower." (Perhaps we are defining "higher" and "lower"
differently. I've been
using "higher" to mean more preferable, though I imagine the actual
ranking number actually gets "lower" as the rank moves closer to #1.)
-Spencer
Roy Nasstrom wrote:
[Winona Online Democracy]
To Winona Online:
For those wish details--perhaps exhaustive and exhausting details--for
my previous statements.
Roy Nasstrom
----- Original Message ----- From: "Roy Nasstrom" <[EMAIL PROTECTED]>
To: "Spencer Madsen" <[EMAIL PROTECTED]>
Sent: Tuesday, April 12, 2005 1:27 PM
Subject: Re: [Winona] Instant Runoff Voting (IRV): Local Costs and
Examples
Spencer, the accompanying article gives one
explanation of the problem in
the section titled "Compromise." I include other sections that may be
relevant. It is an unlikely event unless a particular bloc of voters is
highly organized, a situation generally more likely in partisan than in
nonpartisan elections. Similar tactics are not unknown under current
election rules. (If the information below doesn't come in, let me know
and
I'll try to send it as a full attachment)
Roy Nasstrom
>From Wikipedia, the free encyclopedia.
(Redirected from Instant runoff voting)
When the single transferable vote voting system is applied to a
single-winner election it is sometimes called instant-runoff voting
(IRV),
as it is much like holding a series of runoff elections in which the
lowest
polling candidate is eliminated in each round until someone receives
majority vote. IRV is often considered independently of multi-winner
STV
because it is simpler and because it is the most widely advocated
electoral
reform in the USA.
Instant-runoff voting is also known as Ranked Choice Voting (RCV), a
term
useful for describing the voter's experience as well as the appearance
of
the ballot.
Outside the USA, IRV is known as the Alternative Vote, preferential
voting,
single-winner STV, or the Hare System, though there is room for
confusion
with some of these terms since they can also refer to STV in general.
IRV is used to elect the Australian House of Representatives, the lower
houses of most of Australia's state parliaments, the President of
Ireland,
the Papua New Guinea National Parliament, the Fijian House of
Representatives, and the Parliament of Nauru. See below for a more
detailed
list.
[edit]
How IRV works
[edit]
Voting
Each voter ranks at least one candidate in order of preference. In most
Australian elections, voters are required to rank all candidates. In
other
elections, votes may be "truncated", for example if the voter only
ranks his
first five choices.
[edit]
Counting the votes
First choices are tallied. If no candidate has the support of a
majority of
voters, the candidate with the least support is eliminated. A second
round
of counting takes place, with the votes of supporters of the eliminated
candidate now counting for their second choice candidate. After a
candidate
is eliminated, he or she may not receive any more votes.
This process of counting and eliminating is repeated until one
candidate has
over half the votes. This is equivalent to continuing until there is
only
one candidate left. However it is possible, with voter truncation, for
the
process to continue until there is only one candidate left, who does
not end
up with more than half the votes.
[edit]
An example
Imagine an election for the capital of Tennessee, a state in the United
States that is over 500 miles east-to-west, and only 110 miles
north-to-south. In this vote, the candidates for the capital are
Memphis,
Nashville, Chattanooga, and Knoxville. The population breakdown by
metro
area is as follows:
a.. Memphis: 826,330
b.. Nashville: 510,784
c.. Chattanooga: 285,536
d.. Knoxville: 335,749
If the voters cast their ballot based strictly on geographic proximity,
the
voters' sincere preferences might be as follows:
42% of voters (close to Memphis)
1.. Memphis
2.. Nashville
3.. Chattanooga
4.. Knoxville
26% of voters (close to Nashville)
1.. Nashville
2.. Chattanooga
3.. Knoxville
4.. Memphis
15% of voters (close to Chattanooga)
1.. Chattanooga
2.. Knoxville
3.. Nashville
4.. Memphis
17% of voters (close to Knoxville)
1.. Knoxville
2.. Chattanooga
3.. Nashville
4.. Memphis
City Round 1 Round 2 Round 3
Memphis 42 42 42
Nashville 26 26 26 0
Chattanooga 15 15 0 0
Knoxville 17 17 32 32 58
Chattanooga, having the smallest vote, is eliminated in the first
round. All
of the votes for Chattanooga have Knoxville as a second choice, so they
are
transferred to Knoxville. Nashville now has the smallest vote, so it is
eliminated. The votes for Nashville have Chattanooga as a second
choice, but
as Chattanooga has been eliminated, they instead transfer to their
third
choice, Knoxville. Knoxville now has 58% of the vote, and it is the
winner.
In a real election, of course, voters would show greater variation in
the
rankings they cast, which could influence the result.
[edit]
Special cases of IRV eliminations
Instant Runoff Voting as an ideal does not explicitly define how to
handle
special cases such as ties and different rules can be considered. A
good IRV
election must define rules to handle these cases before the votes are
cast.
The reason why is that there are cases where one set of rules will
select a
winner different from another set of rules and the set of rules used
may
affect how the voters cast their ballots.
Especially when performing IRV counts on smaller elections, there can
be
frequent last-place ties that prevent clear bottom elimination.
Here are some approaches to consider, individually and combined. The
first
class of rules allows many candidates to be eliminated at the first
count
regardless of actual ties. These are practical rules before the first
round
that reward stronger candidates among the full set of competition. Such
rules won't likely affect the winner but they will reduce the number of
elimination rounds and thus the number of opportunities for ties to
develop.
A second class of rules consider actual ties that can't be avoided.
a.. Consider multicandidate elimination of weak candidates as the
first
step:
a.. CANDIDATE COUNT: Define a maximum number of candidates that can
survive the first round.
a.. Example top-two
b.. VOTE MINIMUM: Define a minimum vote threshold (5 vote for
example)
and eliminate all weaker candidates together.
a.. Requires limitations for rule to apply
c.. PERCENT MINIMUM: Define a minimum percent vote threshold (5% for
example) and eliminate all weaker candidates together.
a.. Again, requires limitations for application
d.. PERCENT RETENTION: Define a minimum percent of votes by top
candidates to be retained.
a.. Example - retain the top set of candidates who combined
control
50% of the vote
a.. Tie-breaking rules:
a.. LOGIC: If the tied candidates combined have fewer votes than the
next highest candidate, the entire tied set can be eliminated at once.
a.. Logically deterministic, but may not apply
b.. LAST ROUND: Eliminate the candidate in the tie with the least
votes
from a previous round.
a.. Traditional rule; violates purity of one-person, one vote
ideal
c.. ALL: Eliminate all tied candidates at once.
a.. Good for weak candidates(<5% votes), but violates
independence of
clones which causes IRV implementations using this method to not be
spoiler
proof
d.. RANDOM: Eliminate one randomly to break the tie.
e.. ORDER: If the order of the candidates on the ballot paper has
been
determined by lot, then ties can be eliminated by chosing say the top
candidate.
f.. Random Voter Hierarchy (RVH)
(http://alumnus.caltech.edu/~seppley/MAM%20procedure%20definition.htm):
Randomly determine a strict ordering of the candidates and when
selecting a
candidate to eliminate, pick one based on this strict ordering.
a.. Similar to random elimination, but with many nice properties
not
found with random elimination
[edit]
Where IRV is used
The single-winner variant of STV is used in Australia for elections to
the
Federal House of Representatives, for the Legislative Assemblies
("lower
houses") of all states and territories except Tasmania and the
Australian
Capital Territory, which use regional multi-member constituencies. It
is
also used for the Legislative Councils ("upper houses") of Tasmania and
Victoria, although the latter will switch to the multi-member variant
from
2006. The multi-member variant of STV is used to elect the Australian
Senate
and the Legislative Councils of New South Wales and South Australia in
statewide constituencies, and of Western Australia in regional
constituencies.
Ireland uses STV to elect its own parliament and its delegation to the
European Parliament (by the multi-member variant), and its President
(by the
single-member variant). Northern Ireland also uses the multi-member
variant
for elections to its Assembly and for its European Parliamentary MPs.
Malta
uses the multi-member variant for its parliamentary elections.
In the Pacific, the multi-member variant of STV is used to elect the
parliament of Nauru, while the single-member variant is used for the
Fijian
House of Representatives. Papua New Guinea has also decided to adopt it
for
future elections, starting in 2007. The Fijian system has been modified
to
allow for both "default preferences", specified by the political party
or
candidate, and "custom preferences", specified by the voter. Each
political
party or candidate ranks all other candidates according to its own
preference; voters who are happy with that need only to vote for their
own
preferred candidate, whose preferences will automatically be
transferred
according to the ranking specified by the candidate. Voters who
disagree
with the ranking, however, may opt to rank the candidates according to
their
own preferences. In the last election, about a third of all voters did
so.
The ballot paper is divided by a thick black line, with boxes above
(for the
default options) and below (for customized preferences).
The countries mentioned above all use STV for some or all of their
municipal
elections. Starting in 2004, some municipal areas in New Zealand also
adopted STV to elect mayors (by the single-member variant) and
councillors
(by the multimember variant). Political parties, cooperatives and other
private groups also use STV and/or IRV.
The single winner version of IRV is also used to select the winning bid
of
both the Summer and Winter Olympics in the International Olympic
Committee.
See Table of voting systems by nation
[edit]
Adoption in the United States
Suggested by Robert's Rules of Order, instant-runoff voting is
increasingly
used in the United States for non-governmental elections, including
student
elections at many major universities.
Notable supporters include Republican U.S. Senator John McCain and 2004
Democratic presidential primary election candidates Howard Dean and
Dennis
Kucinich. The system is favored by many third parties, most notably the
Green Party and the Libertarian Party, as a solution to the "spoiler"
effect
third-party sympathizers suffer from under plurality voting (i.e.,
voters
are forced to vote tactically to defeat the candidate they most
dislike,
rather than for their own preferred candidate). In order to increase
awareness of the voting method and to demonstrate it in a real-world
situation, the Independence Party of Minnesota tested IRV by using it
in a
straw poll during the 2004 Minnesota caucuses (results favored John
Edwards).
This dilemma rose to attention in the United States in the 2000
election.
Supporters of Ralph Nader who nevertheless preferred Democrat Al Gore
to
Republican George W. Bush found themselves caught in a dilemma. They
could
vote for Nader, and risk Gore losing to Bush, or, they could vote for
Gore,
just to make sure that Bush is defeated. It has been argued that Bush
won
largely due to the "spoiler effect" of Nader supporters in Florida.
In March 2002, an initiative backed by the Center for Voting and
Democracy
passed by referendum making instant runoff voting the means of electing
local candidates in San Francisco. It was first used in that city in
Fall of
2004. (Note: The San Francisco Department of Elections
(http://www.ci.sf.ca.us/site/election_page.asp?id=24269) prefers the
term
"Ranked Choice Voting" because "the word 'instant' might create an
expectation that final results will be available immediately after the
polls
close on election night.") The new system did not work as well as was
hoped
due to software and logistical difficulties; the results took several
days
to produce definitive results.
In September 2003, an amendment to the California State Constitution
was
proposed (SCA 14
(http://info.sen.ca.gov/pub/bill/sen/sb_0001-0050/sca_14_bill_20030912_introduced.html))
with wide-ranging goals of election reform, including ranked-choice
voting
for statewide offices.
A group in Ferndale, Michigan (http://www.firv.org) is attempting to
implement IRV for mayoral elections in that Detroit suburb.
Washington State has an initiative seeking ballot access in 2005 (I-318
(http://www.irvwa.org/)) that would change the state primary system to
IRV.
[edit]
Assessing IRV
[edit]
Comparison of IRV to normal runoff votings
Advantages to instant runoff ballot: (IRV)
a.. FEWER GAMES: Voters and parties have less opportunity for playing
games in early round(s) to influence the elimination order in favor of
easier competition. (Runoffs allow more flexibility in tactical votes,
influencing elimination, and still having a chance to move back to a
favorite in the final round)
b.. MORE POSITIVE: Candidates are discouraged from negative
campaigning.
(A winning candidate will usually need first, second and lower ranked
preferences to win, and can't safely afford to make enemies with no
second
chance vote)
Advantages to sequential balloting: (runoff voting)
a.. EASIER TO VOTE: A runoff allows voters and factions to refocus
their
attention on remaining candidates in each round. (In IRV, voters must
make
careful choices among a large set of candidates in one ballot and may
not
have enough information to make informed rankings among the competitive
candidates.)
b.. CHANCE FOR APPEAL: Candidates that were eliminated are given
another
chance to endorse and remaining candidates have another chance to court
voters supporting the eliminated candidates.
[edit]
Effect on parties and candidates
Unlike runoff voting, however, there are no chances to deal in between
rounds, change voters' minds, or gain support of the other candidates.
Giving them only one chance to do so, instant runoff preference voting
encourages candidates to balance earning core support through winning
first
choice support and earning broad support through winning the second and
third preferences of other candidates' core supporters. As with any
winner-take-all voting system, however, any bloc of more than half the
voters can elect a candidate regardless of the opinion of the rest of
the
voters.
This is considered a weakness by the advocates of a more deliberative
democracy, who point to the French system of presidential election
where
such between-round dealings are heavily exploited and useful (they say)
to
draw together a very factionalized electorate. However, critics of the
French runoff system point to the dreaded "votez escroc, pas facho"
(vote
for the crook, not the fascist) phenomenon, which awarded Chirac an
undeserved landslide victory in 2002.
[edit]
Flaws of IRV
IRV meets few of the formal voting system criteria defined by political
scientists for assessment of voting systems. Although the
Gibbard-Satterthwaite theorem shows that all reasonable voting systems
allow
for some form of tactical voting, the scope and impact of tactical
voting
varies a lot for different systems.
IRV is unusual in that it does not satisfy the monotonicity criterion
-in
some situations, if a voter or group of voters decides to rank a
preferred
candidate lower, it can result in that candidate winning the election,
whereas if they had ranked the candidate higher, according to their
sincere
preference, that candidate would not have won.
These theoretical objections correspond with several serious practical
'failure modes' for IRV, discussed below. The first two, compromise and
push-over, are common forms of tactical voting, where voters must
change
their preferred ranking of candidates to increase the likelihood of a
favored outcome. Traditional plurality elections are also vulnerable to
'compromise' tactical voting. The other failure modes are more specific
to
IRV.
It should be noted that Condorcet methods can avoid the Return of the
'3rd-party spoiler effect' and Failure to pick a good compromise
problems.
[edit]
Compromise
Assume the earlier Tennessee example. If the voters from Memphis
suspect
that they do not comprise half of the voters and that Memphis is the
last
choice of all other voters, they can "compromise" by ranking Nashville
over
Memphis, and thus ensure that Nashville, their second choice, will win,
rather than Knoxville, their last choice.
Alternatively, if the voters from Memphis are unlikely to vote
tactically
(because they think they have a chance of winning outright or for any
other
reasons), voters from Nashville can improve their result by
"compromising"
and ranking Chattanooga over Nashville. This would allow Chattanooga to
defeat Knoxville in the first round and go on to become eventual
winner, a
better result for Nashville voters than a Knoxville win.
[edit]
Push-over
Tactical voters can intentionally promote "push-overs", candidates
unlikely
to win, past their real preference. This can sometimes benefit voters
by
bringing their preferred candidate to a more winnable final runoff
round,
basically using the push-overs as a shield for protection of their
primary
vote.
[edit]
Return of the '3rd-party spoiler effect'
IRV only stops the '3rd-party spoiler effect' as long as the 3rd party
clearly does not have a chance to win. Just when the 3rd party grows to
a
competitive size, voters may start to find again that they benefit from
tactically ranking a major party candidate over their favorite
candidate.
This failure mode occurs if the voter fears that his 1st-choice
candidate
(the 3rd party) might first win from his best-liked major party, then
not
get enough of the redistributed votes, and finally almost certainly
lose to
the other major party. The voter would wind up with his least-favored
outcome. The voter may seek to prevent this by ranking the best-liked
major
party over his actual first choice.
The following example is given on [ElectionMethods.org
(http://electionmethods.org/)]:
Suppose my true preference is for the Libertarian first and the
Republican
second. Suppose further that the Libertarians are the strongest "minor"
party. At some round of the IRV counting process, all the candidates
will be
eliminated except the Republican, the Democrat, and the Libertarian. If
the
Libertarian then has the fewest first-choice votes, he or she will be
eliminated and my vote will transfer to the Republican, just as I
wanted.
But what if the Republican is eliminated before the Libertarian? Unless
all
the Republican votes transfer to the Libertarian, which is extremely
unlikely, the Democrat might then beat the Libertarian. If so, I will
have
helped the Democrat win by not strategically ranking the Republican
first.
[edit]
Failure to pick a good compromise
IRV can ignore a good compromise in favor of a polarized choice that
enjoys
smaller actual support.
This failure mode occurs in a 3-choice election where parties A and B
are
bitterly opposed, and party C is first choice for a minority but
tolerable
for a large majority. For a real-life example, consider the
17th-century
Europe struggle over "goverment-enforced Catholicism" versus
"government-enforced Protestantism", with "freedom of private worship"
as
the compromise C.
Voting turnout would resemble the following:
38% of voters 38% of voters 11% of voters 13% of voters
1. A 1. B 1. C 1. C
2. C 2. C 2. A 2. B
3. B 3. A 3. B 3. A
In IRV, the compromise (choice C) is eliminated immediately. Choice B
is
elected, giving severely lower total satisfaction amongst voters than
choice
C.
[edit]
Logistical issues
Ballots in IRV cannot be easily summarized. (Political scientists call
this
the Summability criterion.) In most forms of voting, each district can
examine the ballots locally and publish the total votes for each
candidate.
Anyone can add up the published totals to determine the winner, and if
there
are allegations of irregulaties in one district only that district
needs to
be recounted.
With IRV, each time a candidate is dropped, the ballots assigned to
them
must be re-examined to determine which remaining candidate to assign
them
to. Repeated several times, this can be time-consuming. If there is a
candidate X who got more votes than all of the candidates who got less
than
X put together, then all of these candidates who lost to X can be
dropped
simultaneously without affecting the final outcome, which can speed up
counting.
If counting takes place in several places for a single IRV election (as
in
Australia), these counting centers must be connected by a securely
authenticated channel (historically the telgraph was used) to inform
them
which candidate has come last and should be dropped. Centralizing the
counting to avoid this problem can add opportunity for tampering.
[edit]
----- Original Message ----- From: "Spencer Madsen"
<[EMAIL PROTECTED]>
To: "Roy Nasstrom" <[EMAIL PROTECTED]>
Sent: Tuesday, April 12, 2005 11:25 AM
Subject: Re: [Winona] Instant Runoff Voting (IRV): Local Costs and
Examples
Please forgive the truncation: I was
specifically interested in the single
comment below.
Why would voters choose to rank a preferred candidate lower (rather
than
higher)? The lower you rank a candidate the less likely it is that
your
vote will go to that person (because all your higher choices have to be
eliminated from contention before that lower ranked vote becomes
active).
-Spencer Madsen
Roy Nasstrom wrote:
[Winona Online Democracy]
It does have some problems. Under most versions, it is possible that in
a
multi-candidate election a bloc of voters could deliberately rank a
candidate lower than others in order to give him/her a better chance of
winning.
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