The government could save as much as $122m on a postal vote by looking to existing, more representative, polls

Marriage equality: why an opinion poll may be more accurate than a voluntary postal vote

If the government really wanted to determine whether or not Australians support ​marriage equality, it might be better off commissioning an opinion poll rather than running a voluntary postal vote.



Or it could just save the money and look to existing polls, including some already funded by the government, and move on to a vote in parliament.



Postal plebiscite on marriage equality would cost 'up to $122m' Read more

In an effort to break the Coalition’s internal deadlock on same-sex marriage, the government announced it would again attempt to pass legislation for a national plebiscite, and if it were again blocked by the Senate, it would run a postal vote instead.



According to the government, the postal vote on same-sex marriage would be voluntary, cost as much as $122m, and would run for two months.



But a voluntary postal vote may not be representative of Australian views on the topic.



Compulsory voting captures the views of the vast majority of Australians, with the exception of those who are unable to vote, those who deliberately spoil their ballot or those who make a mistake on their ballot.



Opinion polls, such as the weekly polls that determine who you would vote for if an election were held today, only sample a small number of people relative to the ​ population. But people who run surveys often use techniques to try to ensure that this sample is indicative of the greater population. For example, they can select people randomly but from specific groups or areas (known as stratified sampling) and also ensure that the results are adjusted to be representative in line with the demographics of entire population (this is known as weighting).



A voluntary postal ballot would reach a large number of people but the results would be skewed towards the type of people who are inclined to read their mail, those who decide to take part in such a ballot, and those who have their current address on the electoral roll. Essentially, the people who respond would not necessarily be representative of the entire population.



As Malcolm Turnbull himself once pointed out in a piece arguing against postal voting to elect delegates to a constitutional convention, this would affect specific segments of society:



A postal ballot of necessity will only reach voters who are living at the address recorded on the electoral roll … not unless they ring up and make a special request, and who will get around to doing that? This will particularly hurt young people, many of them students, who move more often than older people settled in families. It will also disfranchise Aborigines from remote communities who are often highly mobile.

The participation of a voluntary postal ballot would also be dependent on campaigning from various groups – not just convincing people which way to vote but reaching those who need to update their addresses, those who might be unaware of a vote, and those who might need assistance to vote.



There are also questions about how age might affect postal ballot participation. I haven’t been able to find much on this with postal votes, but Dr Kevin Bonham has an excellent, in-depth blog post on the various ways the postal vote might be skewed.



As it turns out we already have a large, government-funded survey that has asked Australians for their views on marriage equality. The latest Household, Income and Labour Dynamics in Australia ​survey, conducted by the University of Melbourne, found that the majority of Australians believe homosexual Australians should have the same rights as heterosexual Australians, with 59% of men supporting equal rights and 67% of women.



The 2016 Australian Election Study, run by the Australian National University, found a similar level of support, with 70% of people supporting same-sex marriage. Opinion polls from other organisations have found similar results.



What happens after the plebiscite bill is reintroduced is in no way straightforward, as BuzzFeed’s Lane Sainty has demonstrated with this helpful diagram:



Lane Sainty (@lanesainty) Here are the possible outcomes going forward... pic.twitter.com/1vKAafHPu4

There’s also a potential high court challenge to the postal vote and, once it’s all done, the parliament still has to vote on marriage equality, and government politicians are not bound to vote in line with the postal ballot result.

