This year, when anxiety about privacy is high and the census form is filled in online rather than by looking a data collector in the eye, how does the bureau know when you're lying?

Sometimes, it's obvious.

Take the 16 people in Australia who claimed during the last census in 2011 that they were born in Antarctica.

This small group of Antarctic-Australians can be found in Noble Park, Sunbury and Reservoir.

At least one was doing fine in 2011 and was earning more than $2000 a week, although others were in dire financial straits and reported having a negative income. And while they are only in their 20s or 30s, half of them haven't received Australian citizenship yet, and several have already been widowed.

Of course, these people weren't really born in Antarctica. (Fun fact: 11 people have actually been born in Antarctica, in Chilean and Argentinian research bases).

We can't be certain any of the additional information they entered was accurate. Every time the census is sent out a small proportion of people take the opportunity to invent an outlandish new persona for themselves.

As demographer Glenn Capuano of consultancy .id puts it, in every census you find a 99-year-old Indigenous person who was born in Burkina Faso.

He said the optional religion question attracts the most troll answers, with thousands opting to class themselves as Jedis - the fictional religious order from the Star Wars films.

At last count five years ago, there were 64,390 Jedis nationwide, which means there were more followers of The Force than there were Jehovah's Witnesses or Mormons.

Mr Capuano says people also commonly put their religion as 'Pastafarian', 'Collingwood', 'beer' or 'chocolate'.

But all rigorous surveys - even country-wide ones - have some safeguards in place to make sure the outliers get filtered out.

Any self-respecting survey taker knows there are biases that can creep into the data, and can sniff out any responses that smell a bit off.

But the Victorian director of the census, Annette Kelly, says incorrect census responses are more likely to be because of honest mistakes than punters spinning deliberate untruths.

She maintains the vast majority of Australians take the census seriously and fill it out correctly.

And in any case, she says, the bureau conducts logical checks on the data collected. "We don't just push the data through," Ms Kelly said.

For example, the 16 Australians born in Antarctica were flagged as inaccurate, while the out-of-the-box data on religion bundled all the Jedis in with the "not stated" category.

So if you try to make any outrageous claims on the census, they won't be fooled.

If Twitter is anything to go by, they might not be taking the names of respondents at face value.

And even the lies tell the bureau something. They know, for example, that sardonic guys in their 20s are most likely to make stuff up when they fill out the forms.