This paper details House of Representatives by-elections held from 14 September 1901 (Darling Downs) to 6 September 2008 (Lyne and Mayo), a period during which there were 144 by-elections, an average of 3.5 per parliament. The number of nominations has grown over the years from 2.2 per by-election to 10.4 per by-election, and in only four cases was a by-election contested by just a single candidate. Sixty-seven of the by-elections followed the death of the member, 71 members resigned, there have been five voided elections, and one MP was expelled from the House.

The report identifies an increasing tendency for governments to avoid contesting by-elections in their opponents’ safe seats. In only seven cases has the Opposition party failed to contest a by-election.

Since 1949 most by-elections have been caused by the resignation of the sitting member and have occurred in safe seats. On 35 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 4.0 per cent. Since 1949 the largest two-party swing against a government occurred in Canberra in 1995. The largest swing to a government occurred in McPherson in 1981.