Since the introduction of parliamentarism in Sweden, six national referendums have been held. Legal provisions for referendums were introduced in 1922, one year after the adoption of universal suffrage. The Constitution of Sweden provides for binding referendums (concerning changes to the constitution), but all referendums held as of 2012 have been non-binding. The latest referendum, on adopting the euro, was held on 14 September 2003.
The Riksdag decides if a referendum is to be held, when it is held, and the wording of the issue on the ballot. Riksdag also interprets the results (sometimes the outcome is not clear cut, e.g. the nuclear power referendum of 1980).