The wholly unexpected election of a Democratic Labor Party candidate to the Victorian upper house last month has produced a number of over-reactions, based on the mistaken belief that the DLP might “control” the Legislative Council. But it has also drawn attention to the operation of what’s called the multi-member, quota preferential, single transferable vote method of proportional representation, better known as STV PR.

Many commentators have questioned the fairness of a system by which the DLP candidate for the Western Victoria Region could get elected with 2.6 per cent of the vote when the quota for election was supposed to be 16.67 per cent. The reason, of course, is that he received a very favourable flow of preferences - especially from the DLP’s long-term sworn enemy, the Australian Labor Party.

Australians are very familiar with the way preferential voting operates in most of the nation’s lower houses. But if some of the comments about the DLP’s recent good fortune are any guide, we are not as knowledgeable about its operation in proportional systems.

STV can have a very significant, and sometimes surprising, impact on election results. “Surplus” preferences from the major parties, left over after the initial group of candidates that received them has secured as many seats that it is going to get, flow through to other parties, sometimes in unexpected ways. So, too, do the preferences of candidates who fail to secure a quota.

Put simply, in STV systems preferences can flow from both successful and unsuccessful candidates whereas in preferential systems it is only the unsuccessful who have their preferences distributed.

When it adopted STV PR for the upper house in 2003 Victoria decided to follow what has been the Senate practice since 1984 and divide the ballot paper into two sections: “above” and “below” the line. To cast a valid vote above the line an elector merely has to place the number 1 in the box of their party of choice, but if the elector decided to go below the line he or she had to rank at least five candidates, that is, the number of places to be elected in each region. This optional preferential system is not available at Senate elections, where a full set of preferences is mandatory. Not surprisingly, the majority of voters opt for above the line - usually 95 per cent in the Senate and a slightly lower 90 per cent at the 2006 Victorian poll.

But when choosing the convenience of voting above the line electors need to be aware that they thereby endorse the preference allocation on their party’s registered how-to-vote card. Invariably pre-election negotiations among parties - the much derided “preference deals” - influence the make-up of the cards.

The DLP’s election has sparked recriminations within the Labor Party as to why it directed preferences to its ancient enemy, but this largely misses the point. The voting system effectively requires parties to direct preferences so that their supporters cast valid votes, and since not all other parties can be allocated second preferences rank ordering is essential.

In STV systems the major parties try to anticipate which party or candidate is least likely to win election so that their surplus preferences exhaust in a losing camp rather than assist in the election of an enemy. But with Victorian upper house electorates containing over 300,000 voters (and some Senate electorates containing millions) this is a very inexact science and it is easy to make wrong judgements about likely winners and losers.

It took over two weeks of counting before the possibility of the election of DLP candidates became apparent, but the parties were required to lodge their how-to-vote cards with the Victorian Electoral Commission on 17 November. When it came to the last count for the fifth place in the Western Victoria Region the DLP’s Peter Kavanagh was in fifth place with only 10,500 votes, but by the end of the count he was in first place with 95,000 - all because of the churn of preferences.

Of course, we have seen this happen before, but not often. In 2004 Family First’s Steve Fielding was elected to a Senate place in Victoria despite polling only 1.9 per cent of the primary vote. The Nuclear Disarmament’s Robert Wood achieved the same feat in NSW in 1987 with 1.5 per cent. With the increasing number of parties and candidates contesting elections more candidates in STV systems might win with only a miniscule proportion of the vote.

If this is a concern then there are two possible solutions. We could follow the practice of some European countries and require candidates to achieve a threshold of primary votes - say, 5 per cent - to permit them to remain in the count. Those falling short of the threshold would be eliminated and their preferences distributed. But when this idea was floated a few years ago by Senator Helen Coonan it was attacked as being partisan.

Ironically the Victorian version of STV offers a better solution. Why not abolish above the line voting and use optional preferential voting as the sole method of electing the Legislative Council, thereby giving the people and not party managers control over what happens to their vote?