In law, a quorum is the minimum number of members of a deliberative body necessary to conduct the business of that group. Ordinarily, this is a majority of the people expected to be there, although many bodies may have a lower or higher quorum.
When quorum is not met, a legislative body cannot hold a vote, and cannot change the status quo. Therefore, voters who are in favor of the status quo are able to use an obstructive strategy called, in the United States, quorum-busting. If a significant number of voters choose not to be present for the vote, the vote will fail due to lack of quorum, and the status quo will remain.
A quorum in a legislative body is normally a majority of the entire membership of the body. If there are vacancies, that fact is not considered. Thus, a quorum of a legislative body that has 100 seats would be 51 (more than half of 100), even if some seats are vacant. However, it is also common in a legislative body to have a rule that the lack of a quorum does not affect the proceedings unless a point of order is raised.
A quorum in the House of Commons is forty.
The Quorum was a select group of the Justices of the Peace in each county in the Early Modern Period. In theory they were men experienced in law, but many of quorum were appointed because of their status. Some legislation required the involvement of a member of the quorum, (e.g. granting a licence to a badger). In practise increasingly were not qualified, as the proportion in the quorum rose faster than proportion who were called to the bar or practising lawyers. By 1532 an average 45% of Justice of the Peace nationally were of the quorum. In Somerset the proportion rose from 52% in 1562 to 93% in 1636. By then most of those not on the quorum were new to the bench. Sometimes Justice of the Peace were removed from the quorum as a disciplinary measure less drastic than removal from the bench.
According to Article One of the United States Constitution, the United States House of Representatives and the United States Senate each have a quorum of a simple majority of their respective members, except in the case of choosing the President or Vice President when the electoral college fails to obtain a majority vote for a single candidate. In this instance, a quorum of 2/3 is necessary for each house, respectively. The Senate has the additional requirement in Rule VI of its standing rules of a "majority of the members duly chosen and sworn."
The IRS requires 501(c)(3), non-profit organizations to have a quorum present at their required, yearly meetings. If it is not, then not only can they not vote, but they must also have another meeting.
A prominent example of quorum-busting occurred in 2003, when the Texas House of Representatives was going to vote on a redistricting bill that would have favored the Republicans in the state. The House Democrats, certain of defeat if a quorum were present, chose not to be present in the House that day, but instead took a plane to Oklahoma, preventing the bill from passing due to a lack of a quorum. Legislative bodies often have rules to discourage quorum-busting. In many U.S. legislative bodies, such as the United States Senate and House of Representatives, if there is no quorum present a call of the house could be ordered, which would cause absent members to be arrested and brought to the floor of the body. This was the reason that the Killer D's fled to Oklahoma, which is outside of the jurisdiction of Texas law. The Killer D's effectively killed the legislation by staying in Oklahoma long enough to let the legislation expire.
The same year, the Texas Eleven, of the Texas Senate, fled to New Mexico to prevent a quorum of the Senate to prevent another redistricting bill during a special legislative session. Though the Democrats stayed in New Mexico for 46 days, one democrat returned to Texas, creating a quorum; because there was now no point in staying in New Mexico, the Texas Eleven Minus One returned to Texas to oppose the bill with votes in opposition. The bill ultimately passed both the House and the Senate as the 2003 Texas redistricting legislation, which was ruled constitutional by the US Supreme Court in 2006, though Congressional District 23 was deemed an unconstitutional case of gerrymandering.
The technique of the disappearing quorum (refusing to vote although physically present on the floor) was used by the minority to block votes in the US House of Representatives until 1890.
In Canada, the Constitution Act 1867 sets quorum for sittings of the House of Commons at 20 members. If a member calls for quorum to be counted and a first count shows there are fewer than 20 members, bells are rung to call in the members; if after 15 minutes there are still fewer than 20 members, the session is adjourned to the next sitting day; the members present sign a roll on the table of the house, and this list is included in the Journal of the House. There is no need for quorum when the attendance of the House is requested in the Senate, for example when Royal Assent is being given to bills.
Sections 22 and 39 of the Australian Constitution set the quorum for sittings of the House of Representatives and Senate at one-third of the whole number of MPs and senators respectively. Parliament is permitted to change the quorum for each House by ordinary legislation.
In the House of Representatives, the quorum was amended down to one-fifth by the House of Representatives (Quorum) Act 1989, which means the quorum of the current House of 150 Members is thus 30 Members. In the senate, the quorum was amended down to one-quarter by the Senate (Quorum) Act 1991, that is, 19 senators are required to meet the quorum. The quorum includes the occupant of the Chair and is not reduced by the death or resignation of a member or senator.
If at the beginning of a sitting the quorum is not met, the bells are rung for five minutes and a count is then taken; if the quorum is still not met the sitting is adjourned until the next sitting day. During the sitting, any MP or senator may draw attention to the lack of quorum in which the bells are rung for four minutes, and if a quorum is still not met the sitting is adjourned.
Although quorum-busting is virtually unheard of in Australia, proceedings can be disrupted by a member who consistently draws attention to the lack of quorum and there have been some suggestions to enact rules to restrict this practice; however, this is very difficult due to the explicit mention of a quorum in the constitution. It is considered disorderly to call attention to quorum when one exists and members or senators who do so can be punished.
When votes are held in large online communities, where it may never be the case that a majority of the members are "present", the effect of quorum is different. Being absent from the vote no longer requires particular effort, but is the default case: voters are usually assumed to be absent unless they cast a vote. Online communities therefore tend to have quorums that are much less than a majority of the members.
In such votes, a non-monotonic aspect can be introduced: a voter can inadvertently swing a vote from failing to passing by voting "no", if a majority has voted "yes" and that "no" vote is the one that causes quorum to be met. With no penalty for being absent, voters are faced with a strategic choice between voting "no" and not voting.
The Debian project has addressed this issue in its voting mechanisms with the idea of per-option quorum. A quorum is not set on the total number of votes, but on the number of votes a particular option (besides the status quo) must receive before it is considered. For example, in a yes/no vote, the quorum may say that at least 40 "yes" votes are required, along with "yes" having a majority of votes, for the vote to pass.
Quorum, n. A sufficient number of members of a deliberative body to have their own way and their own way of having it. In the United States Senate a quorum consists of the chairman of the Committee on Finance and a messenger from the White House; in the House of Representatives, of the Speaker and the devil.-- Ambrose Bierce (1842 - 1913) The Devil's Dictionary