There are three types of elections in Denmark: elections to the national parliament (the Folketing), local elections (to municipal and regional councils), and elections to the European Parliament. Referendums may also be called to consult the Danish citizenry directly on an issue of national concern. Parliamentary elections are called by the Monarch on the advice of the Prime Minister, usually three to four years after the last election, although early elections may occur. Elections to local councils (municipal or regional) and to the European Parliament are held on fixed dates. Elections use the party-list proportional representation system. All Danish citizens, living in the Kingdom of Denmark and at least 18 years of age, are eligible to vote in parliamentary elections and long-time residents may vote in local elections. The Kingdom of Denmark (including the Faroe Islands and Greenland) elects a unicameral parliament, the Folketing, on a national level. Of the 179 members of parliament, the Faroe Islands and Greenland elect two members each, 135 are elected from ten multi-member constituencies on a party list PR system using the d'Hondt method and the remaining 40 seats are allocated to ensure proportionality at a national level. To get a share of supplementary seats a party needs to get at least 2% of the total number of votes. Only parties that reach any one of three thresholds stipulated by section 77 of the Folketing (Parliamentary) Elections Actwinning at least one constituency seat; obtaining at least the Hare quota (valid votes in province/number of constituency seats in province) in two of the three provinces; or obtaining at least 2% of the national votemay compete for compensatory seats. Denmark has a multi-party system, with numerous parties in which no one party often has a chance of gaining power alone, and parties must work with each other to form coalition governments and/or minority cabinets. Elections to the Folketing must be held at least every four years.