The census, like all ABS data, is collected and published in geographical divisions as defined by the Australian Statistical Geography Standard (ASGS).

It was found that excluding names reduced the accuracy of the data; individuals were more likely to leave questions blank.

[6] Following a public consultation process before the 2016 census, it was found that Australians expected the ABS to hold their information for as long as there is a benefit to the community, and should be destroyed as soon as that need no longer exists.

The capsule is stored securely at the National Archives for 99 years after each census and is released publicly at the end of that period.

It was widely believed at the time of the referendum, and is still often said, that section 127 meant that Aboriginal persons were not counted in Commonwealth censuses before 1967.

In fact section 127 related to calculating the population of the states and territories for the purpose of allocating seats in Parliament and per capita Commonwealth grants.

[13] Thus the Commonwealth Bureau of Census and Statistics interpreted section 127 as meaning that they may enumerate Aboriginal persons but that they must be excluded from published tabulations of population.

Aboriginal persons living in settled areas were counted to a greater or lesser extent in all censuses before 1967.

[a] At the first Australian census in 1911 only those Aboriginal persons living near white settlements were enumerated, and the main population tables included only those of 50 percent or more non-Aboriginal descent.

[16] Prior to 1947, Torres Strait Islanders were regarded as Aboriginal and excluded when not of 50 percent or more non-Aboriginal descent.

The classification is based on the self-perceived group identification approach, using a self assessed response to a direct question.

The questions posed in the colonies were not uniform and Henry Heylyn Hayter, who conducted the Victorian census, found that this caused difficulties in dealing with Australia-wide data.

[21] At the time, the Northern Territory was part of South Australia and had 3,451 white people plus 6,346 Aboriginals in settled districts.

During World War II, the ophthalmologist Norman McAllister Gregg began to investigate the connection between birth defects and the infection of mothers early in their pregnancy.

In 1951, prompted by Gregg's work, Australian statistician Oliver Lancaster examined the census figures of 1911, 1921 and 1933.

He found a peak in the level of deaf-mutism in the age cohort born in 1898 and 1899 and that this matched with a known outbreak of rubella in those years.

"This was the first time in the world that the link between rubella and congenital problems with unborn children was firmly established.

One of the significant findings of the 1921 census was the low rate of males to females in the 20–30 age group, showing the impact of World War I on the population.

Following the 1967 referendum removing section 127 from the Constitution, the "race" question was re-designed for the 1971 census and methods for remote area collection examined to improve identification of Indigenous Australian groups.

For the first time, respondents were given the option of completing an online "eCensus" as opposed to the traditional paper-based version.

During the 24-hour period of 8 August (census night), eCensus delivered more than 12.5 million page views and at 8:47 pm, more than 55,000 households were logged on simultaneously.

IBM assisted with the development of the eCensus, having provided similar infrastructure and technology for the Canadian census earlier that year.

[36] Reflecting this new preference, the tagline of the ad campaign for the census was the rhyming slogan "Get online on August 9".

Letters were sent to each dwelling with unique code numbers that people would need to either login to the census website or order a paper form if they preferred.

The first was that the retention of names and addresses increased to up to 4 years, from 18 months in the 2006 and 2011 censuses, leading to concerns about privacy and data security.

[42][43][44] The Australian Signals Directorate was assisting the ABS to bring the infrastructure back online more than 24 hours after the closure.

[43] On the same day, Prime Minister Malcolm Turnbull stated his displeasure over the event, which had "been a failure of the ABS", with his expectation that "heads will roll" once a review was complete.

[49] It released its findings on 24 November: no individual party was found to be responsible but it was shared between the government, IBM, and other sub-contractors.

Once collection was complete, the ABS issued an announcement which confirmed that in spite of the initial online problems, there was a preliminary response rate of more than 96%.

The 2021 Census achieved a response rate above the Australian Bureau of Statistics target obtaining data from 10 million (10,852,208) dwellings.