In 1986, Murray Goot of Macquarie University was commissioned by the NSW Parliamentary Library to produce a background paper on by-elections. What was originally to be a brief paper became a thorough historical and statistical study of New South Wales by-elections. Goot’s study is still the most substantial analytical work on the subject in Australia political science literature.

In the short time allowed for the preparation of the current paper, it has not been possible to repeat the work carried out by Goot. No attempt has been made to update Goot’s work on the age of members and candidates, nor to model the predictive capacity of by-election swings.

This paper has confined itself to updating Goot’s tables on the causes of by-elections, the periods for which seats have been left vacant, as well as the swings recorded at by-elections. Where appropriate, data from Goot’s tables have been included, and commentary has been provided on where Goot’s findings continue to be relevant to more recent by-elections, and where new trends appear to have developed.

Goot’s study included all by-elections from 1941 up to and including Bass Hill and Rockdale in August 1986. This publication has concentrated on by-elections since 1965, updating Goot's data with three further by-elections conducted in the term of the Unsworth Government, as well as all by-elections held during the Greiner, Fahey and Carr Governments. Details of by-elections between 1941 and 1965 can be found in Goot’s study.

Data for all by-elections since 1965 have been re-calculated from a database of election results currently being prepared as part of the Sesquicentenary celebrations for the New South Wales Parliament. Apart from a few minor corrections in the calculations, there are no significant differences from the data in Goot’s publication. Only one change from Goot’s study is worth noting. In Goot’s Table A1, an incorrect date has been corrected and a change in number of candidates has been included for the 1975 Pittwater by-election. Correcting this makes only the slightest change to Goot’s other tables.