since 1 october 1973, northern ireland is made of 26 districts. each district has a council which looks after local services. the 26 districts are made of 582 wards. each ward elects 1 councillor. there 582 councillors in northern ireland and there is an election every 4 years. the voting system used to elect each councillor is single transferable vote. some of the councils are known as "borough" or "city" councils. every year, each council elects a chairman. in "borough" and "city" councils, the chairman is called the mayor. in belfast city council, the chairman is called the lord mayor. in "borough" and "city" councils, up to 25% of councillors are given the title alderman.