Background: In the 2013 Australian Federal election, several parties were elected to the senate seemingly because of usability issues related to the ballot paper (see here for discussion). For example:
[The] Australian Sports Party has no policies other than advocating lots of sport, and won just 0.22 per cent of the vote. But with preferences from other small parties, they are likely to get a Senate quota ahead of the second Labor candidate, who had 12.33 per cent.
For those unfamiliar with the Australian federal electoral system, the Senate is the upper house. Each state has an equal number of senators. Election to the senate requires that you achieve a certain percentage of votes in a given state. It is a preferential block voting system. Thus, you can achieve the required votes after preferences have been allocated.
On the current ballot, you can either vote above the line or below the line. Above the line involves ticking a single box and accepting the allocation of preferences of that particular party. Ticking below the line requires that you number every candidate from one to the number of candidates (which could be over 100). Thus, the according to wikipedia about 98% of people vote above the line.
A strange situation arose in the 2013 election where several micro-parties appear to have won senate seats due to a flaw in the combination of the preferential and the above the line system. This seems to have been brought on by a range of factors including a general across the board increase in the vote for micro-parties and collaboration in micro-parties in allocating preferences to each other. Traditionally, when the likely senator was one of only a few parties, the allocation of preferences was fairly clear. However, many voters if explicitly asked about their preferences, may have put one of the major parties above some of the more obscure parties that seem to have been elected based on preferences.
Thus, there is a problem:
- There are too many candidates to make it easy for people to indicate their preferences for all candidates.
- The preferences implied by putting a 1 in a box "above the line" (i.e., accepting the preferences of a given party) may often not be consistent with what a voter would intend their preferences to be were they asked to think about it.
- What is a good way to design ballot papers with a large number of candidates in a preferential system so that it is easy to use and conveys the important aspects of people's preferences?
- What psychological theory or empirical research justifies such a ballot paper?