Voting Rules for

Different uses for voting need different types of voting.

Voting rules for setting policies; Condorcet rules

Agenda Scams & Errors

The common agenda rules are inherently erratic in their results and that is closely related to some types of manipulation. These often result in less popular policies. The tricks, loopholes and errors are numerous. Newer rules relieve some common ones described here.

Defects in Agenda Voting

Meetings often make interlocking decisions 1 at a time through yes-no voting, with or without explicit rules of order, agendas, and votes. Decisions at the top of an agenda can make later options impossible or moot. Sometimes within 1 decision, the later an option is introduced, the fewer rivals it must defeat, as shown in an example below.

Many times participants may talk about all options at once but never clearly tell (vote) their second and third choices -- so a small interest group united on a single proposal can appear to be the strongest group. And an individual with a good compromise but no ardent supporters might drop it from the discussion. Good voting rules avoid all these problems.

Manipulation of Agenda Voting

Here are some of the ways legislative rules let reps abuse their power:

Council members know each others' priorities and control the options on a ballot. So they can routinely devise proposals to split the opposition. These factors make manipulations effective and likely. Good legislative voting rules have features to reduce manipulation, making them more complex than electoral rules. (An earlier page looked at manipulation of elections by candidates or voters.)

A) Late introduction: The later an option is introduced, the fewer alternatives it must defeat (but items at the top of an agenda can make later options moot). This defect may occur by chance or by design. Phillip Straffin gives an example in which any 1 of 4 options can win depending on the agenda's order of proposals.

Table III    3 Ballots
Rank 1 2 3
1st A C B
2nd B A D
3rd D B C
4th C D A

Table IV    Agenda Orders and Outcomes
First Vote Second Vote Third Vote
B versus A
A wins
A vs. C
C wins
C vs. D; D wins 
 the final tally. 
C vs. B B vs. A A vs. D; A wins.
A vs. C C vs. B B vs. D; B wins.
B vs. A A vs. D D vs. C; C wins.

B) Pareto Criterion: In the first case D wins even though the voters are unanimous in preferring B over D. Thus sequential pairwise voting sometimes violates the “Pareto Criterion” which states that if all voters prefer B over D, a voting rule should not produce D as the winner.

C) Insincere ballots: The second agenda chose A, the last choice of voter 3. He can come out better by voting insincerely for C on the first vote instead of his true preference for B. The result would be B versus C, C vs A, C vs D, D wins.

“Our third voter has thus achieved his second choice instead of his last choice by this judicious bit of insincerity, and in the process has produced a rather undesirable social outcome. Sequential pairwise voting invites voters to think strategically and vote insincerely.”
from Topics in the Theory of Voting.

Agenda 1, D wins
  Agenda 1, D wins

Agenda 2, A wins
  Agenda 2, A wins

Agenda 3, B wins
  Agenda 3, B wins

Agenda 4, C wins
  Agenda 4, C wins

Agenda 2 3rd_voter_insincere, D wins
  Agenda 2 3rd_voter_insincere, D wins

D) One against all: Pitting 1 against all, often the status quo versus all proposed changes, requires the 1 to beat an alliance of all others. Therefore the 1 can lose even if most people like it more than any other 1.

E) Poison-pill amendment: To reduce support for a bill, opponents may attach a poison-pill amendment, often taking a good idea too far. Some who backed the amendment then join those who opposed it; together they defeat the amended bill.

F) Free-rider amendment: An unpopular item can win if it is amended or "attached" to an essential bill.

G) Phony solution, dilution: When torn on an issue loved by voters but hated by corporations, some reps try to have it both ways:  they water down the bill with amendments, then vote for the meaningless measure. It is hard for a voter to uncover which reps cause the most damage.

(Several books in the bibliography give examples of these and other problems.)

Democracy requires a clear, concise public record of each rep's votes on legislation, so voters have the information they need to rank their reps. A rep's preference ballot ranks all competing proposals. This shows a rep's choices more clearly to most people than a series of votes on unfamiliar parliamentary procedures.

A Condorcet tally of preference ballots reduces all of these problems. But it can be manipulated into a sort of tie. Breaking those ties fairly is the next topic.  Voting cycles

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