The EBRC's terms of reference are issued by the Prime Minister, and are not embodied in legislation. In giving recommendations for boundary changes over the years, the Committee has considered various factors, including using hill ridges, rivers and roads as boundaries rather than arbitrarily drawn lines; and the need for electoral divisions to have approximately equal numbers of voters so that electors' votes carry the same weight regardless of where they cast their ballots. In 1963, the EBRC adopted a rule allowing the numbers of voters in divisions to differ by no more than 20%. The permitted deviation was increased to 30% in 1980. It is up to the Cabinet to decide whether or not to accept the Committee's recommendations.