text: Elections are usually by thirds ( a third of the seats elected , three years in every four ) , although the 2004 elections , due to substantial boundary changes ( which involved the total number of councillors reduced ) , saw all seats contested .
simplified: A third of the seats elected , three years in every four . In the 2004 elections , due to a lot of boundary changes ( which involved the total number of councillors reduced ) all seats were contested .