Belgium is a constitutional, popular monarchy and a federal parliamentary democracy. The bicameral federal parliament is composed of a Senate and a Chamber of Representatives. The former is made up of 50 senators appointed by the parliaments of the communities and regions and 10 co-opted senators. Prior to 2014, most of the Senate's members were directly elected. The Chamber's 150 representatives are elected under a proportional voting system from 11 electoral districts. Belgium has compulsory voting and thus maintains one of the highest rates of voter turnout in the world.