Tolerable chance or undesirable arbitrariness? Distributing surplus votes under PR-STV

Electoral reform is not simply a matter of moving from one system to another. There are variations in the workings of each particular system and it is important for reformers to consider the consequences of each of these variations. For parliaments considering the system of proportional representation by the single transferable vote (PR-STV), as operates in Ireland, one such detail concerns the method of distributing surplus votes. This article highlights the problem of how this operates in a random fashion in the Irish Dáil, one of the few national parliaments using PR-STV. To do this, the first method involves an analysis of transfer patterns at Irish elections since 1980. The second method is a simulation of election results using the actual electronic voting returns of 150,000 voters from three constituencies at the 2002 Irish general election. It is found that there is an undesirable degree of arbitrariness involved, which has the potential to produce an outcome that violates social choice concerns and elect different parliamentarians.