This weekend, Queenslanders are being urged to “just vote 1” by the Liberal National government, just as Labor has done in the past. Premier Campbell Newman warned that “wasted votes going to independents and minor parties” could see Labor win the election.

But is that really true that you can waste a vote under Queensland’s electoral rules? And is numbering only one box on your ballot paper the most effective way to have your say under the system?

How Queensland and NSW are different

Unlike the other Australian states and territories, Queensland and NSW both use the optional preferential voting system to elect their lower house MPs. Queensland has no upper house of review.

That’s in contrast to federal elections, which use compulsory preferential voting for the lower house – meaning all the boxes have to be numbered in order of preference for a vote to count.

Under the optional preferential system, voters may indicate a preference for only one candidate or they may vote for some or all candidates on the ballot paper in order of their preference.

By voting for some or all candidates in order of preference, voters can ensure that their vote is not wasted if their first choice of candidate is not elected, because their vote will be reallocated to the candidates they gave a second or subsequent preference to.

Voters in Queensland who wish to support an independent or minor party may do so even if that candidate is unlikely to be elected, knowing they can allocate their preferences to other candidates they are willing to support.

Unlike the compulsory preferential system used at federal elections they do not have to allocate preferences to all candidates. This can result in a preference being used to elect a candidate the voter does not support.

Why Queenslanders have options

Queensland state elections have used optional preferential voting (OPV) since 1992. As the Electoral Commission of Queensland explains in its OPV fact sheet, it wasn’t entirely new to the state: a form of OPV was also used from 1892 to 1942.

Queensland switched to optional preferential voting after the Fitzgerald Inquiry into corruption in Queensland raised questions about the existing system and recommended the establishment of an Electoral and Administrative Review Committee to examine the electoral system’s fairness.

Optional preferential voting was among several recommendations from that committee. The Goss government brought in the change to OPV in time for the 1992 state election.

Two advantages of the optional preferential system are that it allows voters to support only candidates they wish to vote for, and it minimises unintentional invalid voting.

But optional preferential voting had not been the policy of either major party. By not requiring 50% + 1 of the vote, it became a little easier for minor parties and independents to get elected, although they still had to gain the largest number of votes. It also meant that the major parties would have to work harder to ensure voters allocated preferences on to them.

In 1992 after optional preferential voting was introduced, most voters (73%) allocated more than one preference, while 23% just voted for one candidate.

Now the opposite is now true.

How many people just vote 1?

ABC election analyst Antony Green has charted the rapid rise of the “just vote 1” phenomenon on his blog, showing that a clear majority of Queenslanders now vote for only one candidate (69.9% at the 2012 election, as shown below), compared to those who number all the boxes (26.4%) or number only some (3.6%).

The sharpest change came after then-premier Peter Beattie urged people to “just vote 1” to advantage Labor against the divided conservatives in 2001. It’s a tactic that the LNP has now adopted too.

In this 2015 election, votes for Katter’s Australia Party, the Palmer United Party, One Nation and a group of independents could all potentially undermine support for the LNP, while the Greens and independents could do the same for the ALP.

Both major parties are telling voters to support them first to ensure stable government – but this is not necessarily true. Queensland has had stable minority governments led by both the Liberal Nationals and the ALP, supported respectively by independents Liz Cunningham and Peter Wellington.

How to make your vote count

Votes cast for independents and minor parties don’t have to be wasted under Queensland’s optional preferential voting system – as long as you understand how it works.

The major parties have often argued that such a vote favouring independents or minor parties is “wasted”, since they have a much lower rate of success than major parties. Alternately, it is sometimes said that that even if your favoured independent/minor party candidate is elected, they’re unlikely to have much influence, or – worse – create “chaos” by undermining strong governance.

Voting for a minor party or independent candidate has three possible outcomes.

The first is that the chosen candidate is elected, meaning the voter’s intention is fulfilled.

A second option is that the voter has allocated second and subsequent preferences to other candidates they support. In that case, if their first choice is not elected, one of those other candidates may be, which ensures the voter has had some influence on the outcome.

The third option is that the voter either votes one without allocating any preferences, or else numbers only some of the boxes, and their vote ends up being removed from the count.

This may be seen as a wasted vote by the major parties – and as a voter, you might agree, if it wasn’t your intention to exhaust your vote in that way.

However, other voters may deliberately do exactly that, as a way of exercising their choice not to vote for candidates they do not support.

Voters in Queensland can best ensure their votes are not wasted by allocating preferences to those candidates they support. Don’t just vote 1: vote in order of preference for all those candidates you want to support.

Read more of The Conversation’s Queensland election 2015 coverage.