Geography and election results: Disproportionality and bias at the 1993-2004 elections to the Australian house of representatives

The Alternative Vote system used for elections to the Australian House of Representatives is generally believed to disadvantage the Australian Labor Party in contests with the Liberal and National parties. However, most analyses on which such conclusions are based over-simplify the situation by not separating out the translation of votes into seats according to whether the election outcome in a district is determined using the first-preference or two-party preferred (2PP) votes. Analyses of bias at five recent elections which recognise that separation find little bias against either party in the districts where the determination used the 2PP votes (i.e. no candidate received a majority of the first preferences), but considerable bias in those where the outcome was decided on first-preferences. Furthermore, that bias was not in one direction, but rather favoured the largest party in each of those contests. The reason for this is identified in the geography of support for the two parties, which produces the equivalent of a 'cracked gerrymander' in sufficient districts to have a significant impact on the outcome.