this is how many votes it took last Thursday to elect a County Councillor in Devon

Conservative 2,787

Liberal Democrat 5,043

Labour 5,805

Independent 9,234

Green 14,142

Why does the Conservative party take almost twice as many councillors per vote as labour and the Lib Dems, and five times more than the Green Party?

(Votes cast were Conservative 108,702 taking 39 seats, Liberal Democrat 45,395 winning 9 seats, Labour 40,640 winning 7 seats, Independent 27,707 winning 3 seats, Green 28,285 winning 2 seats)