Opponents of Senate voting reform in 2016 focused a lot of attention on the danger of votes exhausting – which happens when a voter hasn’t marked a preference for any of the remaining candidates.
The rate of exhausted votes was relatively low in 2016, but that didn’t stop exaggerated claims about exhausted votes being a problem before the 2019 election.
The voting system does make it much easier to exhaust your ballot, as a side-effect of making it much easier for voters to mark their own preferences rather than relying on the discredited system of group voting tickets. Yet this problem was significantly reduced by a policy of encouraging voters to number at least six boxes above the line or twelve boxes below the line (which was what AEC staff were meant to tell voters, was printed on ballots, and was advocated for on most how-to-votes).
So what happened in 2019? Exhausted vote rates went down nationally, although the rate did increase in two states.
The exhaustion rate depends on a number of factors: the number of candidates and groups (the more boxes on the ballot paper, the more you need to fill out to minimise the exhaustion risk), the number of seats to be elected, and the partisan balance at the conclusion of the count.
The ballot paper was much smaller in 2019, in part due to the half-Senate election. The rate of just-vote-1 ballots remained very low (although it went up slightly) with most people still marking 6 preferences on their Senate ballot.
There was a substantial increase in the exhaustion rate in Victoria and a small increase in South Australia. The rate dropped in the other four states, in particular in New South Wales and Western Australia.
While exhaust rates were consistently higher in bigger states, where a larger ballot meant that a standard six preferences would be less likely to ensure a vote that didn’t exhaust, it appears the trends may have something to do with who was standing at the final round (ie. candidates who were either elected without distributing their surplus, or were the last candidate to be excluded).
The Greens were still standing at the end of the count in NSW, Queensland and Western Australia, while Labor’s Lisa Singh was still standing in Tasmania. But there was no Labor or Greens candidate in the count at the end in Victoria and South Australia.
One Nation were still standing in five states at the end of the count. In South Australia the last three candidates were Liberal, United Australia and One Nation. A left-wing voter wouldn’t have had many options. In Victoria, the last three were Liberal, One Nation and Derryn Hinch.
All of this analysis is based on the proportion of the total vote which has exhausted by the end of the count. Many of those exhausted votes would have already helped elect someone before exhausting, so even fewer voters would have had their vote exhausted without contributing to the election of a senator.
The overall conclusion is similar to in 2016: most votes helped elect someone, or ended up with the last candidate to be eliminated. As long as voters mostly mark multiple preferences, exhaustion rates will stay low. It will also help if ballot papers continue to shrink as we move further away from the group voting tickets era. The new Senate system is working reasonably well to ensure that most votes count.