Hare quota

Use in STV

In an STV election a candidate who reaches the quota is elected while any votes a candidate receives above the quota in many cases have the opportunity to be transferred to another candidate in accordance to the voter's next usable marked preference. Thus the quota is used both to determine who is elected and to determine the number of surplus votes when a person is elected with quota. When the Droop quota is used, often about a quota of votes are not used to elect anyone (a much lower proportion that under the first-past-the-post voting system) so the quota is a cue to the number of votes that are used to actually elect someone. The Hare quota was devised by Thomas Hare, one of the first to work out a complete STV system. The number of votes in the quota is determined by the district magnitude of the district in conjunction with the number of valid votes cast.

Example

Suppose an STV election using the Hare quota has two seats to be filled and three candidates: Andrea, Brad, and Carter. One hundred voters voted, each casting one vote and marking a back-up preference, to be used only in case the first preference candidate is un-electable or elected with surplus. There are 100 ballots showing preferences as follows:

Because there are 100 voters and 2 seats, the Hare quota is:

${\displaystyle \frac{100}{2}=50}$

To begin the count the first preferences cast for each candidate are tallied and are as follows:

• Andrea: 60
• Brad: 26
• Carter: 14

Andrea has reached the quota and is declared elected. She has 10 votes more than the quota so these votes are transferred to Carter, as specified on the ballots. The tallies of the remaining candidates therefore now become:

• Brad: 26
• Carter: 24

At this stage, there are only two candidates remaining and one seat open. The most-popular candidate is declared elected; the other is declared defeated. Although Brad has not reached the quota, he is declared elected since he has more votes than Carter. The winners are therefore Andrea and Brad.

Use in party-list PR

Hong Kong, Brazil, and Guyana use the Hare quota in largest-remainder systems. Costa Rica uses a modified Hare quota for its Legislative Assembly. In Brazil's largest remainder system the Hare quota is used to set the basic number of seats allocated to each party or coalition. Any remaining seats are allocated according to the D'Hondt method. This procedure is used for the Federal Chamber of Deputies, State Assemblies, Municipal and Federal District Chambers.

In Hong Kong

For geographical constituencies, the SAR government adopted weakly-proportional representation using the largest remainder method with Hare quota in 1997. Typically, largest remainders paired with the Hare quota produces unbiased results that are difficult to manipulate; however, the combination of extremely small districts, no electoral thresholds led to a system that parties could manipulate using careful vote management. By running candidates on separate tickets, Hong Kong parties aimed to ensure they received no seats in the first step of apportionment, but still received enough votes to take several of the remainder seats when running against a divided opposition. The Democratic Party, for example, filled three separate tickets in the 8-seat New Territories West constituency in the 2008 Legislative Council elections. In the 2012 election, no candidate list won more than one seat in any of the six PR constituencies (a total of 40 seats). In Hong Kong, the Hare quota has effectively created a multi-member single-vote system in the territory.

Mathematical properties

In situations where parties' total share of the vote varies randomly, the Hare quota is the unique unbiased quota for an electoral system based on vote-transfers or quotas; however, if the quota is used in small constituencies with no electoral threshold, it is possible to manipulate the system by running several candidates on separate lists, allowing each to win a remainder seat with less than a full quota. This can make the method behave like the single non-transferable vote in practice, as has happened in Hong Kong. By contrast, rules based on the Droop quota cannot be manipulated in the same way, as it is never possible for a party to gain seats by splitting.