The term ranked voting, also known as preferential voting or ranked choice voting, pertains to any voting system where voters use a rank to order candidates or options—in a sequence from first, second, third, and onwards—on their ballots. Ranked voting systems vary based on the ballot marking process, how preferences are tabulated and counted, the number of seats available for election, and whether voters are allowed to rank candidates equally. An electoral system that utilizes ranked voting employs one of numerous counting methods to determine the winning candidate or candidates. Additionally, in some ranked voting systems, officials mandate voters to rank a specific number of candidates, sometimes all; while in others, voters may rank as many candidates as they desire.
The instant-runoff voting method is commonly employed for the election of single members using ranked votes. Conversely, the election of multiple members using ranked votes typically utilizes single transferable voting (STV). There exist other systems applicable for single-member selection or multi-member elections. Ranked voting in multi-member districts plays a part in national elections in Australia, Ireland, Malta, and the United Kingdom—specifically, the Scottish and Welsh Parliaments. On the other hand, single-winner ranked voting is used in the election of national-level politicians from the states of Maine and Alaska within the United States. Ranked voting is also utilized in Nauru. For certain local elections in New Zealand, ranked voting is used. Moreover, in the United States, some cities, counties, and federal primaries across 16 states, as well as 5 additional states' overseas voters for federal elections, employ ranked voting.
A form of ranked voting was also used in Slovenia for electing the two minority representatives; it was replaced by the first-past-the-post system in 2021.
History of ranked voting
The earliest mention of ranked voting can be traced back to the works of Ramon Llull in the late 13th century. His interpretations, however, are not universally clear, and he is often believed to have favored Copeland's method, which used a series of pairwise elections instead of ranked-choice ballots. His ideas eventually caught the attention of Nicholas of Cusa in the early 15th century, who appeared to develop independently what is now known as the Borda count method that utilizes ranked ballots. The writings of both Llull and Nicholas were lost, only to be rediscovered in the 20th century.
The modern analysis of ranked voting commenced when Jean-Charles de Borda published a paper in 1781, advocating for the method that now bears his name. This methodology drew criticism from the Marquis de Condorcet, who developed his own method to determine collective preference, asserting that Borda's approach did not always reflect the group's preference. However, his example remains a point of contention (see Comparison of electoral systems).
Interest in ranked voting was renewed in the 19th century. Danish pioneer Carl Andræ formulated the Single Transferable Vote (STV) system, which was adopted by his native Denmark in 1855. Simultaneously, Thomas Hare in the UK independently invented STV in 1857. The single-winner variant of STV, known as instant-runoff voting (IRV), was proposed by William Robert Ware around 1870. While Ware might have been unaware, this system was mentioned earlier by Condorcet, albeit only to criticize it.
Ranked voting first saw governmental use in the 1890s in Tasmania, deploying the STV system. Its broader adoption in Australia began in the 1910s. By the 1920s, ranked voting had expanded globally. It was used in Ireland, South Africa, and approximately 20 cities each in Canada and the U.S. Instant-runoff voting was utilized for single official elections, like mayors, while STV was employed for multiple official elections, such as councillors or school board trustees. Moreover, ranked voting was also adopted for governmental elections in Ireland, Malta, and Canada (specifically Alberta and Manitoba) beginning in the 1920s.
Theoretical exploration of electoral processes was initiated by a 1948 paper from Duncan Black, which was soon followed by Kenneth Arrow's research on the consistency of voting criteria. This subject has since continued to receive scholarly interest under social choice theory, typically falling within the economics discipline.