Electoral Distortion in New Zealand

Abstract

are to be congratulated on developing yet further the analysis of the relation of seats to votes.1 They note in passing, quite correctly, that in an earlier article on this themes I failed to consider the possibility of isolating and measuring the electoral distortion attributable to inequalities in size of constituencies (the "rotten borough" effect), and to the differential concentration of party voters (the "gerrymander" effect). By coincidence, or trans-Tasman telepathy, this problem had occurred to me shortly before the Soper-Rydon analysis appeared ; since the technique I evolved for dealing with it differs in some respects from theirs, a brief exposition may be of interest.Let us assume an election in which every seat is contested by two major parties, L and N. Suppose, for a given percentage of the (L+N) vote, L would win a total of x seats of mean size P, while with the same percentage N would winy seats of mean size Q. The electoral bias in favour of L is then the difference between the number L actually wins and an even division of the seats, i.e.

Measuring Partisan Bias in Single‐Member District Electoral Systems

“…For example, Soper and Rydon (1958) equate the median vote (i.e., 50%) with what they call the "effective" vote-a term that is now typically reserved specifically for partisan efficiency. Brookes (1959) also starts the derivations of the measures he proposes under the presumption that symmetry is the concept of interest. And while this approach started early, there are more recent examples of authors who adopt symmetry without much further explanation (Altman 2002;Gelman and King 1994b;Jackman 1994;Niemi and Deegan 1978).…”

Electoral Bias at the 2010 General Election: Evaluating its Extent in a Three‐Party System

“…The original method for decomposing electoral bias for a two-party system was pioneered by Ralph Brookes (1959Brookes ( , 1960 and later adapted by others (Mortimore, 1992;Johnston et al, 2001) to accommodate the growing significance of smaller parties. Brookes' basic approach suggests that it is possible to measure the level of bias by comparing the two-party translation of votes into seats at the actual election with a 'notional election' (we prefer the term 'norm for comparison') that either assumes the vote shares are reversed for the two parties or that the election produced a dead heat in votes.…”

Geography and Election Results: Disproportionality and Bias at the 1993–2004 Elections to the Australian House of Representatives

“…A procedure for both assessing the amount of bias and decomposing its sources according to these two major geographies, developed by a New Zealand political scientist (Brookes, 1953; 1959; 1960) is deployed here, but modified to incorporate factors not present in his New Zealand analyses (Johnston et al. , 1999).…”