Electoral system

An electoral system is a set of rules and mechanisms used to determine the results of an election. Electoral systems are used in politics to elect governments and also in non-political settings such as business, nonprofit organizations and informal organisations. These rules govern all aspects of the voting process: when elections occur, who is allowed to vote, who can stand as a candidate, how many votes are cast by each voter, how ballots are marked and cast, how the ballots are counted or weighed, how votes translate into the election outcome (seats), limits on campaign spending, and other factors affect the process. Political elections are defined by constitutions or electoral laws, are typically conducted by election commissions, and may use one or more electoral systems for different offices.

Some electoral systems elect a single winner to a position, such as prime minister, president or governor, while others elect multiple winners, such as members of parliament or boards of directors. When electing a legislature, areas may be divided into constituencies with one or more representatives or the electorate may elect representatives as a single unit. Voters may vote directly for an individual candidate or for a list of candidates put forward by a political party or alliance. There are many variations in electoral systems.

The mathematical and normative study of voting rules falls under the branches of economics called social choice and mechanism design, but the question has also engendered substantial contributions from political scientists, analytic philosophers, computer scientists, and mathematicians. The field has produced several major results, including Arrow's impossibility theorem (showing that ranked voting cannot eliminate the spoiler effect) and Gibbard's theorem (showing it is impossible to design a straightforward voting system, i.e.