Preference Voting under PR-STV 1948–2011

Abstract

Given the seismic shifts that transformed the Irish electoral landscape in February 2011, it is tempting to focus solely on the massive changes in the distribution of first preference votes recorded in that election. However, such an approach would grossly underrate the role of second and subsequent preferences in allocating seats and in uncovering fundamental aspects of Irish voting behaviour.¹ In using these preferences to proceed count by count and elimination by elimination towards the final outcome, proportional representation by the single transferable vote (PR-STV) generates unparalleled additional evidence on how voters relate to the candidates and to the parties. In analysing this evidence, it is important to note several features of the Irish electoral system. In the first place, and contrary to a not uncommon view, in PR-STV each voter has only one vote. Secondly, that vote is transferable, according to the preference order indicated by the voter. Thirdly, although from the point of view of the act of voting, PR-STV is simple and transparent, the mechanics of transferring votes are quite complex. Because the complexities can affect the interpretation of the transfer evidence, the mechanics of PR-STV are addressed in some detail below.