Iceland is an independent republic. Executive power is vested in the president and the government, legislative power in the president and the legislative assembly (Althing). The president is elected by universal suffrage for a four-year term. Effective executive power is exercised by a prime minister enjoying the confidence of the Althing: the prime minister is appointed by the president, and the prime minister in turn selects a cabinet composed of ministers responsible to the Althing for their acts. The president must sign all legislation before it becomes law.
All citizens who have reached the age of 18 may vote, provided they have resided in Iceland for the five years immediately preceding an election. In 2003, 87.5% of Icelanders eligible to vote in the parliamentary elections did so. By a system of proportional representation, voters elect the 63 members of the unicameral (since 1991) Althing from eight constituencies at a general election held every four years, but sooner if the governing coalition loses its ability to command a legislative majority. Because of the widely varying populations of the constituencies (Reykjavik constitutes one-third of the nation's population), each constituency has a minimum of five seats, and more populous regions have more. Three-quarters of the seats in any constituency are divided by the parties according to proportional representation, voters elect the 63 members of the unicameral (since 1991) Althing from eight constituencies at a general election held every four years, but sooner if the governing coalition loses its ability to command a legislative majority. Because of the widely varying populations of the constituencies (Reykjavik constitutes one-third of the nation's population), each constituency has a minimum of five seats, and more populous regions have more. Three-quarters of the seats in any constituency are divided by the parties according to proportional representation of that region, while the final quarter of the seats in each constituency are apportioned according to the national vote tally to ensure national proportional representation. Any citizen qualified to vote is eligible for to run for a seat in the Althing. When any amendment to the constitution is voted, the Althing is dissolved and new elections are held; if the new Althing accepts the proposed amendment, it becomes law when ratified by the president.
The institution of the Althing has parliamentary immunity and its members swear allegiance to the constitution. Government ministers are normally members of the Althing and enjoy full parliamentary privileges. The constitution and the rules of procedure of the Althing specify the rights and duties of parliamentarians, and the legislative year of the Althing begins on 1 October. The legislative agenda of the Althing is divided among 12 standing committees. At the first meeting following the inauguration ceremony, the president of the Althing is elected. In addition to acting as the chief executive of Althing, the president sits on the five-person presidium along with the four vice presidents. The presidium is responsible for the organization of parliamentary activities. Sessions of the Althing are normally held four days a week.