Sweden developed as a constitutional monarchy under the constitution of 1809, which remained in effect until 1 January 1975, when a new instrument of government replaced it. Legislative authority is vested in the parliament (Riksdag). The monarch ceded involvement in power-brokering among the parties as early as 1917 when the Liberals and Social Democrats entered into a coalition. Today, the monarch performs only ceremonial duties as the official head of state; the monarch's last political duty, regular participation in cabinet meetings, was taken away under the most recent constitution. The king must belong to the Lutheran Church; the throne was hereditary only for male descendants until 1980, when female descendants were granted the right to the throne.
The Riksdag was bicameral until 1971, when a unicameral body of 350 members serving three-year terms was established; the 1975 constitution provided for 349 members, and the parliamentary term was lengthened to four years in 1994. All members of the Riksdag are directly elected by universal suffrage at age 18. Voter turnout has traditionally been very high in Sweden, though in the 2002 election turnout dipped to 80.1% compared with turnout over 86% for the previous two elections. Foreign nationals may vote in regional and municipal elections. Elections at all levels are simultaneous and are held the on the third Sunday of September every fourth year. The parties' share of the national vote is directly translated into seats in Riksdag. Interim national elections may be called by the government between regular elections, but the mandate of the interim election is valid only for the remaining portion of the regular four-year parliamentary term of office.
In Sweden's parliamentary system, executive power lies with the government, or cabinet, that is formed by the majority party in parliament or by a coalition of parties. Sweden has also functioned with a minority government in which the largest party does not enjoy a majority in parliament and must form ad-hoc coalitions with other parties in the Riksdag. The cabinet as a whole is responsible for all government decisions and must defend the their legislative agenda in the plenary sessions of the Riksdag. A vote of no confidence by an absolute majority of the Riksdag allows for the forced resignation of individual ministers or of the entire cabinet. A vote of no confidence becomes moot if within one week of the vote if the government calls for new elections for the entire Riksdag.
Chief executive power is wielded by the prime minister, who is formally proposed by the speaker of the Riksdag and confirmed by vote of the parliamentary parties. The prime minister appoints a cabinet usually consisting of 18–20 members reflecting of the party or coalition of parties in power. Once a week the government takes decisions in a formal meeting presided over by the prime minister. The cabinet as a whole discusses all-important decisions prior to taking a decision. After a decision has been taken by the cabinet, the ministers practice collective responsibility in which all support the decision taken by the government. Ministers may issue directives but administrative decisions are taken by central boards, which have their respective spheres of activity delimited by the Riksdag.
National referenda on policy questions of national importance are permitted by the constitution. Sweden's parliament has the highest level of political representation of women in the world; ten of the 22 ministers in the 2003 government were women, and 45% of the Riksdag members are women.