All you'll ever need to know about STV

Q: How did we get this new voting system?

A: Green Party co-leader Rod Donald managed to get it written into law in 2001 as an option for local body elections and to get Labour-Alliance government support.

Q: Why the change?

A: Rod Donald argued that:

A voter turnout of below 50 per cent at the last local body elections in 2001 showed voters were disenchanted with the present First Past the Post system.

The number of mayors elected by a minority of voters highlighted another failure of the old system.

He said Wellington's new mayor, Kerry Prendergast, and re-elected Dunedin mayor Sukhi Turner both won with only 34 per cent of the vote. New Auckland mayor John Banks got 43 per cent as did re-elected Christchurch mayor Garry Moore.

"As a consequence most votes were wasted in those contests," he argued. It also meant main centre New Zealand mayors were in power with the support of less than one-quarter of eligible voters in their area.

Q: Who else uses STV?

A: It is already used in parts of Australia, Northern Ireland and Malta. New Zealand's dairy giant Fonterra has used it to elect its board of directors and and shareholders' council. The Christchurch City Council tried STV a few times in the 1920s and 1930s.

Q: Is STV in New Zealand different?

A: Government sources claim the New Zealand system is too complicated to do by hand, so vote counting will be done using computer software developed by the Department of Internal Affairs. It has been independently audited and certified.

Q: What happens when I vote?

A: Pictured on the left is how a completed voting form might look for a local authority election under STV.

In each election contest the computer will calculate a "quota" - the number of votes a candidate needs to be elected.

In the completed form the voter is saying:

"The candidate I most want to represent me on the council is Sam Jones. He's my number one choice.

"But if he gets more votes than the quota [that is more than he needs to be elected], then part of my vote is to be transferred to my second choice, Ngaire Smith, and maybe this will help her get elected.

"On the other hand, if my favourite Sam Jones has so little support that he can't possibly be elected, transfer my vote to Ngaire Smith."

In other words, poor old Sam Jones is dropped from the list.

Q: What is a valid STV vote?

A: You can rank all the candidates if you wish. On the other hand, as long as a number "1" is clearly marked alongside a candidate's name, that is a valid vote.

Each subsequent preference will also count as long as it follows an unbroken sequence. So a voting paper filled in, say, 1, 2, 4, 5 would be valid only for 1 and 2 as preferences after that are not clear.

Q: How does that differ from First Past the Post?

A: Pictured right is a First Past the Post voting form for the election of three ward councillors.

On the FPP form you can vote for a maximum of only three candidates. If you tick four boxes, it will be impossible for the electoral officer to work out which three candidates you want.

Q: What is this "quota" thing under Single Transferable Vote?

A: The Department of Internal Affairs defines it as the number of votes needed to get elected.

The quota is calculated by the STV computer software, based on the total number of votes and the number of vacant positions. The process treats all candidates the same by giving them a "keep value".

This "keep value" in the election results will show which candidate did best. Here is an example:

If the "quota" (or number of votes needed to be elected) is 100 and the candidate gets only 100 votes, they keep all those 100 votes. So they have a keep value of 1 (100 per cent).

But if a candidate receives 200 votes, that person still needs only 100 votes to be elected. The others can be distributed to other candidates.

In this case the candidates' "keep value" would be 0.5 (50 per cent), because they only need 50 per cent of their votes to be elected. In other words, the most popular candidates in an STV election will have the lowest "keep value".

Q: Who thought this "keep value" up?

A: A British computer scientist called Brian Meek, would you believe. It is part of "Meek's Method, which the New Zealand form of STV is based on. The method was especially designed for STV vote counting by computer because it was held that hand-counting of votes was not feasible given the formulae involved.

Q: Will STV voting be an improvement?

A: Wait and see. Did MMP improve parliamentary behaviour? Do shortened one-day cricket games have improved results under the the Lewis-Duckworth system?