Analysis of the Ballot Shuffling Attack on Irish ballot counting for Proportional Representation by Single Transferable Vote (PR-STV)

TR-2015-188, Author: Dermot Cochran

Analysis of the Ballot Shuffling Attack on Irish ballot counting for Proportional Representation by Single Transferable Vote (PR-STV) 

Abstract:

The current Irish legislation for counting of ballots does not fully comply with the true meaning of proportional representation by single transferable vote. This is due to the way in which second and subsequent transfers are handled, the legislative requirement to only count the last set of ballots transferred and the sensitivity of the counting algorithm to the order in which ballots are shuffled.  A formal model of PR-STV is used to identify scenarios in which the counting under current electoral laws gives a different result compared to what would have happened using another ordering of the same ballots.

Technical report TR-2015-188 in IT University Technical Report Series, August 2015.

Available as PDF.