In social choice theory, the majority rule (MR) is a social choice rule which says that, when comparing two options (such as bills or candidates), the option preferred by more than half of the voters (a majority) should win.
In political philosophy, the majority rule is one of two major competing notions of democracy. The most common alternative is given by the utilitarian rule (or other welfarist rules), which identify the spirit of liberal democracy with the equal consideration of interests. Although the two rules can disagree in theory, political philosophers beginning with James Mill have argued the two can be reconciled in practice, with majority rule being a valid approximation to the utilitarian rule whenever voters share similarly-strong preferences. This position has found strong support in many social choice models, where the socially-optimal winner and the majority-preferred winner often overlap.
Majority rule is the most common social choice rule worldwide, being heavily used in deliberative assemblies for dichotomous decisions, e.g. whether or not to pass a bill. Mandatory referendums where the question is yes or no are also generally decided by majority rule. It is one of the basic rules of parliamentary procedure, as described in handbooks like Robert's Rules of Order. leading to poor deliberative practice or even to "an aggressive culture and conflict"; however, the median voter theorem guarantees that majority-rule will tend to elect "compromise" or "consensus" candidates in many situations, unlike plurality-rules (see center squeeze).
Supermajority rules
Parliamentary rules may prescribe the use of a supermajoritarian rule under certain circumstances, such as the 60% filibuster rule to close debate in the US Senate.
- Anonymity: the decision rule treats each voter identically (one vote, one value). Who casts a vote makes no difference; the voter's identity need not be disclosed.
- Neutrality: the decision rule treats each alternative or candidate equally (a free and fair election).
- Decisiveness: if the vote is tied, adding a single voter (who expresses an opinion) will break the tie.
- Positive response: If a voter changes a preference, MR never switches the outcome against that voter. If the outcome the voter now prefers would have won, it still does so.
- Ordinality: the decision rule relies only on which of two outcomes a voter prefers, not how much.<!--<!--While not as clearly desirable as the other principles are, this condition is needed for strategyproofness, and can also be helpful in situations where cardinal information is unavailable.-->-->
- This can be replaced by strategyproofness, i.e. every person's dominant strategy is to honestly disclose their preferences.
Agenda manipulation
If voters' preferences are defined over a multidimensional option space, then choosing options using pairwise majority rule is unstable. In most cases, there will be no Condorcet winner and any option can be chosen through a sequence of votes, regardless of the original option. This means that adding more options and changing the order of votes ("agenda manipulation") can be used to arbitrarily pick the winner.
Other properties
In group decision-making voting paradoxes can form. It is possible that alternatives a, b, and c exist such that a majority prefers a to b, another majority prefers b to c, and yet another majority prefers c to a. Because majority rule requires an alternative to have majority support to pass, majority rule is vulnerable to rejecting the majority's decision.
Limitations
Arguments for limitations
Minority rights
A super-majority rule actually empowers the minority, making it stronger (at least through its veto) than the majority. McGann argued that when only one of multiple minorities is protected by the super-majority rule (same as seen in simple plurality elections systems), so the protection is for the status quo, rather than for the faction that supports it.
Another possible way to prevent tyranny is to elevate certain rights as inalienable. Thereafter, any decision that targets such a right might be majoritarian, but it would not be legitimate, because it would violate the requirement for equal rights.
<!--Erroneous priorities
The erroneous priorities effect (EPE) states that groups that act upon what they initially consider important almost always misplace their effort. Such groups have not yet determined which factors are most influential. Only after identifying those factors can they take effective action. EPE was articulated by K.M. Dye at the Food and Drug Administration. This discovery led to the recognition that even with good intentions, effective action requires a different paradigm for language and voting. EPE is a negative consequence of phenomena such as spreadthink and groupthink. Effective priorities are dependent on recognizing the influence patterns of global interdependencies and are defeated by EPE when priorities simply aggregate individual stakeholder's subjective voting that does not consider those interdependencies. Dye's work resulted in the discovery of the 6th law of the science of structured dialogic design, namely that "Learning occurs in a dialogue as the observers search for influence relationships among the members of a set of observations."
Under some circumstances, the legal rights of one person cannot be guaranteed without unjustly imposing on someone else. McGann wrote, "one man's right to property in the antebellum South was another man's slavery."
Amartya Sen has noted the existence of the liberal paradox, which shows that permitting assigning a very small number of rights to individuals may make everyone worse off.
Other arguments
Saunders argued that deliberative democracy flourishes under majority rule and that under majority rule, participants always have to convince more than half the group, while under supermajoritarian rules participants might only need to persuade a minority (to prevent a change).