This paper provides details of House of Representatives by-elections, from that held for Darling Downs on 14 September 1901 to the most recent held on 20 October 2018 for Wentworth. The following observations can be made about those by-elections:
- there have been 158 by-elections, an average of 3.5 per parliament.
- the nine by-elections held during the current, 45th, Parliament is the second highest number in an individual parliament—seven of these related to dual citizenship; 10 by-elections—nine caused by the deaths of members—were held during the 20th Parliament (1951–1954) • the average number of nominations has grown over the years from 2.2 per by-election to 11.5 per by-election
- in only four cases was a by-election contested by just a single candidate
- an increasing tendency has been for governments to avoid contesting by-elections in their opponents’ safe seats
- in only ten cases have the opposition party failed to contest a by-election
- eighty-three of the by-elections followed the resignation of the member, 68 members died in office, there have been six voided elections, and one MP was expelled from the House
- since 1949 resignations account for over two-thirds of by-elections and over half the resignations have occurred in safe seats
- on 36 occasions the party complexion of a seat has altered at a by-election; five of the losses have been by the opposition of the day
- the average two-party preferred swing against the government of the day has been 3.8 per cent and
- since 1949 the largest two-party swing against a government (16.1 per cent) occurred against Labor in Canberra in 1995. The largest swing to a government (16.2 per cent) occurred to the Coalition in McPherson in 1981.