Malaysia is a federal constitutional elective monarchy. The system of government is closely modelled on that of the Westminster parliamentary system, a legacy of British colonial rule.[48] The head of state is the Yang di-Pertuan Agong, commonly referred to as the King. The King is elected to a five-year term by and from among the nine hereditary rulers of the Malay states; the other four states, which have titular Governors, do not participate in the selection. By informal agreement the position is systematically rotated among the nine,[48] and has been held by Abdul Halim of Kedah since December 2011.[49] The King's role has been largely ceremonial since changes to the constitution in 1994, picking ministers and members of the upper house.