A blindfolded bureaucrat plucks numbered balls out of a bingo cage to decide the order in which candidates are placed on the ballot paper.

It’s just one aspect of what makes Australia’s voting system unusual – so unusual, in fact, that few other countries in the world use them.

Other quirks include our preferential voting system for the House of Representatives, the even more complex partial preferential voting system in the Senate, and compulsory voting.

So, how does voting work in Australia? Can your vote be wasted? And what does a donkey vote have to do with the blindfolded bureaucrat?

If the barrel roll seems old-fashioned, that’s because it is.

It’s actually written into the hefty Commonwealth Electorate Act of 1918. That act says the public is allowed to watch the draw, and even roll the barrel themselves.

The reason the Australian Electoral Commission does this is to make sure the order of House of Representative candidates and parties for the Senate on the ballot papers are randomised.

They’re randomised because of “donkey” voting. That’s where a voter numbers all the boxes on the ballot paper from top to bottom sequentially.

The commission can never be sure if someone is doing this because they don’t care about voting, or because those are their genuine preferences. So all donkey votes are counted, says commission spokesman Evan Ekin-Smyth.

“Common sense would tell you it’s most likely a donkey vote, but you never know, it could just fall that way.”

An informal vote is different to a donkey vote – and will not be counted. This is where ballots are invalid. They might be left unmarked, or the voter has put a tick or cross instead of numbers, or they have written something on the ballot that identifies them, or they don’t have the required number of boxes unmarked. For example, they put just a “1” and nothing else on their House of Reps ballot. See below.

Australia is one of only two democracies with compulsory voting.

The other is Belgium. In both countries, if people don’t vote on polling day they face a fine. About 20 other countries have mandatory voting, including Brazil, but it’s not enforced with fines.

The commission expects about 91 per cent of eligible Australians to vote. There are 17 million people enrolled.

In other countries, voters may have to number just one box on the ballot for a party or candidate. But to cast a legitimate vote for the House of Representatives in Australia – where members are elected by preferential voting – people need to number each box on the ballot in order of their choice.

This potentially gives voters more say, says Ekin-Smyth. Why?

Say a candidate wins 40 per cent of the first preference vote. It’s a lot, but not enough for a seat. Another candidate might win fewer first preference votes but then receive the majority of second preferences, which would put that person in the lead.

“[The first candidate] might be the favourite for 40 per cent but the least favourite for 60 per cent,” he says.“The idea is that it truly reflects not just people’s most favourite but their least favourite as well.”

Here’s how it works:

For the Senate, more Tasmanians vote below the line than voters in any other state or territory.

About 27 per cent of Tasmanians voted below the line in the last federal Senate election, followed by the ACT with about 22 per cent. Everywhere else, more than 90 per cent of people chose to vote above the line.

Both methods – above the line or below – are perfectly legitimate ways to vote in the Senate. Voters can either number at least six boxes from 1 to 6 above the line, in order of preference; or number at least 12 boxes below the line. They don’t have to mark every single box on the ballot paper, which is why it’s called a partial preferential system. You certainly can number every single box below the line but, depending on your state or territory, you might be there for a while – in 2016, NSW had a record 151 candidates on the Senate ballot.

Unlike the House of Representatives ballot, where people are voting to elect one candidate, the Senate ballot is usually for six seats. A half-Senate election, usually held at the same time as a federal lower house election, means six of the 12 senators who represent each state are up for election; as are two senators each from the ACT and NT.

To win a seat, the party or candidate must get a quota – a proportion of the electorate’s votes based on the number of available seats. For example, if the Nationals win enough votes in NSW to fill two quotas, they get two Senate seats.

Here’s how Senate voting works (there are quite a few steps, toggle right to get to a result):

In the 2019 Senate vote, Malcolm Roberts was elected after receiving just 77 first-preference votes, the lowest number of any federal representative.

How did he get a seat? It was all about the complicated flow of preferences (see the graphic above). Roberts managed to stay just ahead of the other candidates as their preferences were redistributed in each round. From just 77 first preference votes, where voters chose him by name below the line rather than his party, One Nation, above the line, he managed to ride the wave of votes that trickled his way to land in the Senate.

At the same time, most senators who get elected do win enough first preferences to gain their seat on election night.

When we talk about preferences, it’s voter preferences that matter, not a political party’s. You don’t have to follow the how-to-vote cards they give you outside the polling booth. “Nobody directs preferences across parties, except for you, the voter,” says Ekin-Smyth.