<P> In the Senate (the upper house), there are 76 senators: twelve each from the states and two each from the mainland territories (the Australian Capital Territory and the Northern Territory). The House of Representatives (the lower house) has 150 members elected from single - member electoral divisions, commonly known as "electorates" or "seats", allocated to states on the basis of population, with each original state guaranteed a minimum of five seats . Elections for both chambers are normally held every three years simultaneously; senators have overlapping six - year terms except for those from the territories, whose terms are not fixed but are tied to the electoral cycle for the lower house; thus only 40 of the 76 places in the Senate are put to each election unless the cycle is interrupted by a double dissolution . </P> <P> Australia's electoral system uses preferential voting for all lower house elections with the exception of Tasmania and the ACT which, along with the Senate and most state upper houses, combine it with proportional representation in a system known as the single transferable vote . Voting is compulsory for all enrolled citizens 18 years and over in every jurisdiction, as is enrolment (with the exception of South Australia). The party with majority support in the House of Representatives forms the government and its leader becomes Prime Minister . In cases where no party has majority support, the Governor - General has the constitutional power to appoint the Prime Minister and, if necessary, dismiss one that has lost the confidence of Parliament . </P> <P> There are two major political groups that usually form government, federally and in the states: the Australian Labor Party and the Coalition which is a formal grouping of the Liberal Party and its minor partner, the National Party . Within Australian political culture, the Coalition is considered centre - right and the Labor Party is considered centre - left . Independent members and several minor parties have achieved representation in Australian parliaments, mostly in upper houses . </P> <P> In September 2015, Malcolm Turnbull successfully challenged Tony Abbott for leadership of the Coalition, and was sworn in as the 29th Prime Minister of Australia . The most recent federal election was held on 2 July 2016 and resulted in the Coalition's forming a majority government . On 24 August 2018, Turnbull resigned after his party voted for a leadership spill . Treasurer Scott Morrison was elected as party leader and was sworn in as prime minister later that day . </P>

As of the year 2002 has become australia's number one means of economic income