Thanks for your questions, Donn. The number of members in the House of Representatives is determined by the Parliament, on the understanding that there is approximately double the number of Members of the House of Representatives as Senators.
The last change in numbers in the House of Representatives was from 148 to 150 at the 2001 election. This was because there was an increase of representational entitlements for Western Australia and the Northern Territory.
There is no maximum number of people in an electorate. When changes are made to the electoral boundaries in a state or territory (this process is called a ‘redistribution’) each electorate should have approximately the same number of enrolled voters. At this time, the number of voters in each electorate must be within 10% of that state or territory’s average. For example if a state’s average number of voters per electorate is 100,000, then each electorate in that state should have between 90,000 and 110,000 enrolled voters.