Simplify the following text for a Grade 8 native English-speaking person.
Original: 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 .