Getting your head around the complex STV system

Those who ran their campaigns as if it was Fpp...were risking an opportunity to score more modest rankings that could get them over the moving line.

As the dust settles after October’s local body elections, there are some people asking why Palmerston North bothers with the single transferable vote (STV) system.

Some have even blamed the low voter turnout on what seems like a complicated system.

At the end of the day, 39.1 per cent of people voted in the city council elections, which is a tiny bit higher than in 2013.

For those of us who are fascinated by how the system works, the council has helpfully uploaded some numbers which show the inner workings of the STV calculator, and how the final make up of the council was determined.

It shows that for outright favourites like Lew Findlay, Brent Barrett and Tangi Utikere, the process appeared to make no janine.rankin@fairfaxmedia.co.nz

difference to their fortunes.

They all collected more than 1292 votes on the first iteration, and were the first to be elected. They had so many more votes than they needed, that a chunk of their votes trickled down, with their supporters’ second preferences pulling Adrian Broad across the line. They would probably have been the top four polling candidates whether the system had been first past the post (FPP), or STV.

But after that, STV made a difference. On the first count, Labour candidate Lorna Johnson had just 496 first preference votes, way below the quota, and was in 16th place, competing for one of 15 seats. But by the end, she was elected in a creditable 11th position.

The result was no mystery to the Labour team, which had deliberately run an STV campaign, based on their understanding of how STV works to influence sometimes quite different results to the more polarising FPP.

Those who ran their campaigns as if it was FPP and only asked for people’s No 1 vote were risking an opportunity to score more modest rankings that could get them over the moving line.

The Labour team did not individually implore voters to give them their Number 1 vote, understanding that any number at all, especially a reasonably high number, was likely to come into play. They asked people to vote for them as 1, 2, 3 and 4.

And a significant number of people did that, or at least included them in their list. As each of the other three Labour candidates dropped out of contention, their votes were redistributed to others still in the running. By the time the calculator had been through its paces 24 times, Johnson was in 15th position and looking likely to be elected.

Then, when Zulfiqar Butt dropped out of the race, nearly half of the 784-odd votes he had accumulated were transferred to Johnson, boosting her way over the quota, and contributing to her final placing. For another councillor, Aleisha Rutherford, the use of STV did not affect whether or not she would be elected, but it altered her ranking significantly.

On the first count, she was comfortably in the middle of the most likely first 15, sitting in 9th place. But when the youngest candidate Abi Symes dropped out, many of the 687 votes she had accumulated went to Rutherford, the next youngest candidate, who had helped Symes with her campaign.

Rutherford did not need the extra support at that stage, but the system still registered the boost in popularity, and she finished in 5th position.

Johnson, obviously, is a fan of STV. ‘‘It worked for us, because we ran an STV campaign. That was a strategic decision, so we were not surprised by what happened, even if we would have liked to get more of the team elected.’’

She thinks it is a fairer system, delivering more of a ‘‘consensus’’ result, even though it gets hard to follow when there are as many as 28 candidates vying for 15 places. We just kind-of have to trust the software programme.

There’s another interesting thing about what voters choose to do with STV. While all of the advice tells people to rank as many or as few candidates as they wish, a remarkably high 17.1 per cent chose to rank 15, the number of seats on the council. But that number was down from the city’s first STV election in 2013 when 23 per cent of voters ranked 15 people.

Another peak occurred at 28, where 7.1 per cent of voters chose to rank the whole lot, a technique with some value upon which experts disagree.

Only 3.7 per cent voted for just one candidate, suggesting 96.3 per cent of people understood the significance of influencing the make up of the council, rather than the result for their favourite, better than some of the candidates did. The most popular choice was to rank five, which would be a realistic guess of how much one vote or its parts might be likely to bounce around the system until coming to rest.