Australian Bureau of Statistics
2940.0 - Census of Population and Housing - Details of Undercount, 2011
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 21/06/2012
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ESTIMATES OF NET UNDERCOUNT
AGE AND SEX
The likelihood of counting a person in the Census has traditionally varied according to age and sex. As has been observed in previous Censuses (both in Australia and overseas), young adults are the age group who are most likely to be missed in the Census, with young adult males being more likely to be missed than their female counterparts. In contrast, older adults are much more likely to be counted.
Tables 2 and 3, and graph 4, show that this was also true for the 2011 Australian Census. In particular, males aged 20-24 years again had the highest net undercount rate (7.8%) followed by males aged 25-29 years (7.5%). The net undercount rate for females was also highest for those aged 20-24 years (6.0%). While the undercount rate for 25-29 year old females (4.0%) was higher than most age groups, in contrast to 2006 it was noticeably lower than the rate for females in their early 20s.
The lowest net undercount rate was for people aged 55 years and over (-0.1%).
In general, males had a higher net undercount rate (2.2%) than females (1.2%).
STATES AND TERRITORIES
The challenges facing Census enumeration vary between states and territories. Table 5 shows the rates of net undercount for Australian states and territories for Censuses from 1991 to 2011.
As in previous Censuses, in 2011 the Northern Territory recorded the highest net undercount rate of all states and territories (6.9%), while the Australian Capital Territory continued to record the lowest net undercount rate (0.7%).
While the two territories reflected the minimum and maximum net undercount rates, Victoria and South Australia continued to show relatively low rates (both 1.1%). Western Australia had the highest rate for a state (2.5%), emphasising the continued coverage challenges in that state. All states and territories had a lower net undercount rate in 2011 than in 2006, except for Tasmania which was relatively consistent at 2.0%. The greatest decreases were for Queensland (3.7% in 2006 to 1.8% in 2011) and Victoria (2.3% in 2006 to 1.1% in 2011).
It is important to note the effect of the introduction of Automated Data Linking (ADL) when considering the changes from 2006. For more information, see the Statistical Impact of ADL Technical Note (in Explanatory Notes).
GREATER CAPITAL CITY/REST OF STATE REGION
The regional differences in net undercount in the 2011 Census for greater capital cities and the rest of state regions are presented in tables 6 and 7.
Greater capital cities are represented by Greater Capital City Statistical Areas (GCCSAs) and represent a socio-economic definition of each of the eight state and territory capital cities. This means each greater capital city includes people who regularly socialise, shop or work within the city but live in small towns and rural areas surrounding the city. 'Rest of state' regions are the areas within each state or territory not defined as being part of the greater capital city.
Different problems are encountered in enumerating different areas of Australia and these are reflected, to a certain extent, in the net undercount rates. In urban areas, locating dwellings is generally easier but contacting occupants and gaining their cooperation can be more difficult. In contrast, in rural and remote areas where dwellings may be scattered over a wider area, locating the dwellings can cause considerable difficulties. In 2011, New South Wales, Tasmania and the Northern Territory had higher net undercount rates in their rest of state regions compared with their greater capital cities. All other states and territories had a lower net undercount in their rest of state regions (compared to their greater capital cities).
At the broad Australia level, the total net undercount rates in 2011 were slightly lower for the rest of state regions (1.7%) compared to greater capital cities (1.8%). This contrasts with 2006, when the net undercount rate for balance of state/territory (3.0%) was higher compared to the capital cities (2.5%). As was the case in 2006, in 2011 the Northern Territory showed the largest difference in net undercount rate between its greater capital city and rest of state region (3.7% and 10.9% respectively).
It is important to note that for the 2011 PES, the Australian Statistical Geographical Standard (ASGS) replaced the Australian Standard Geography Classification (ASGC) as the framework for PES geography. The move to the new geography will allow for improvements in the quality of small area time series data from the Census. However, the change has resulted in an unavoidable break in series and care should be taken when comparing the 2011 greater capital city/rest of state net undercount estimates to the 2006 capital city/balance of state net undercount estimates.
REGISTERED MARITAL STATUS
Table 8 shows net undercount estimates and rates by registered marital status by sex. The net undercount rates were highest for people identified as never married (3.7%) and lowest for people widowed, divorced or separated (a net overcount of 0.8%). It is important to consider the strong relationship with age when interpreting net undercount estimates by registered marital status.
Special procedures are used in the Census to support the enumeration of the Aboriginal and Torres Strait Islander population, as counting this population continues to present a number of challenges.
The 2011 Census counted 548,147 persons who had been identified as being of Aboriginal and Torres Strait Islander origin, which was 21% more than the 454,799 persons in 2006. A summary of Aboriginal and Torres Strait Islander Census counts is presented in Census of Population and Housing - Counts of Aboriginal and Torres Strait Islander Australians (cat. no. 2075.0), which was also released on 21 June.
The 2011 PES estimated that 662,335 Aboriginal and Torres Strait Islander persons should have been counted in the Census, compared with 513,977 persons in 2006.
Table 9 shows net undercount estimates by Indigenous status. In 2011, the net undercount rate was 17.2%, compared with 11.5% in 2006. The net undercount for 2011 was estimated to be 114,188 persons, which was almost double the 2006 estimate of 59,178 persons.
It is important to note that these measures refer to the undercount of persons according to their Indigenous status, regardless of whether or not they were actually counted in the Census. In other words, persons who were counted in the Census and had a 'not-stated' Indigenous status will not be included in the Census counts of either Aboriginal and Torres Strait Islander or non-Indigenous persons, but are, instead, a separate category for this classification. They will, however, be included in Census counts for other key categories, such as Age and Sex.
In order to understand the differences between the 2006 and 2011 PES results, the ABS undertook an extensive quality assurance process. The results of this process are summarised in the Improvement in collection of Indigenous status Technical Note (in Explanatory Notes).
This quality assurance process has led the ABS to advise caution when comparing net undercount for Aboriginal and Torres Strait Islander persons between 2006 and 2011. Analysis of data indicates that the main contributing factor for the difference between the 2006 and 2011 estimates was improved PES methodology and procedures, which resulted in better identification of Aboriginal and Torres Strait Islander people in the 2011 PES.
Historically, the ABS has a program of continuous improvement in its survey methodologies. Improvements to the PES in 2006 and 2011 are summarised in Survey Enumeration, Linking and Matching and Estimation. While the individual impacts of all improvements made in 2011 cannot be measured, they have resulted in a change in the Indigenous status classification of Aboriginal and Torres Strait Islander persons in the PES and the Census between 2006 and 2011. This has in turn resulted in a noticeably different net category change for Indigenous status in net undercount estimates, and accounted for most of the change in the estimate of net undercount for Aboriginal and Torres Strait Islander persons between 2006 and 2011.
It is also important to note that Indigenous status, as collected in both the Census and PES, is based on responses to a question related to information that some people will consider personal and sensitive. Respondents can choose to indicate in the Census that they are Indigenous or non-Indigenous, or they can choose to not answer the question at all. If no answer is provided, the Census does not impute for this missing response (which is also the case for imputed persons). The Census count is therefore a count of those who were identified by a respondent as Indigenous (i.e. those without a response are excluded).
COUNTRY OF BIRTH
As Census forms are generally completed by one or more persons in a household, those who have come to Australia from other countries and whose first language is not English may find completing a Census form more difficult than other Australians. For several Censuses, special strategies have been employed to promote an understanding of the Census among migrants, in particular that the Government is not using their information for anything other than statistical purposes and to provide assistance in a range of languages.
Tables 10 and 11 show the undercount estimates and rates by country of birth. The countries displayed were the 10 highest ranked (in terms of population residing in Australia) according to the 2011 Census. There were 1,195,432 people (5.6% of the Census count) whose country of birth was not stated in the Census. Since Census does not impute a Country of birth for these people, the PES estimates of net undercount are not adjusted to take account of any imputed persons. As with Indigenous status, these people, while counted in the Census, do not contribute to the Census counts for these categories but do count to PES estimates of their population. For further information about Census not-stated responses and their impact on estimates of net undercount see Components of net undercount.
Of those countries listed, persons born in China had the highest net undercount (55,965 persons) followed by New Zealand (46,536 persons). China also had the highest net undercount rate (14.9%) followed by India (9.7%). Persons born in Scotland had the lowest net undercount rate (1.2%) followed by those born in England and Italy (both 4.6%).
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This page last updated 20 June 2012