APPENDIX 2: DATA AND METHODOLOGICAL LIMITATIONS

GEOGRAPHY

In this article, Census data are analysed and presented at the Local Government Area (LGA) geographical level based on LGA boundaries as at 2011. Data from the 2006 Census has been adjusted according to 2011 LGA boundaries. For more information about LGAs, see: Australian Statistical Geography Standard (ASGS): Volume 3 - Non ABS Structures, July 2011 (cat. no. 1270.0.55.003).

LGAs vary considerably in size and population. For this reason, population turnover rates are expressed relative to the 2006 Census count, adjusted for comparability between the 2006 and 2011 Census populations. In this article, a rate per 1,000 population is used.

Table 1 shows the number of LGAs in each state by the size of their Estimated Resident Population (ERP) as at 30 June 2011. The ERP and land area of LGAs varies significantly between and within each state and territory. For example, Murchison (S), a rural LGA in Western Australia, had an ERP of only 123 people in 2011 and a land area of 45,030.2 km². Yet Stirling (C), an LGA encompassing suburban areas of Perth, had a 2011 ERP of 208,399 people and a land area of 104.7km².

TABLE 1. ESTIMATED RESIDENT POPULATION (ERP) of Local Government Areas, 30 June 20111 ERP < 1 000 No. of LGAs ERP 1 000 - 4 999 No. of LGAs ERP 5 000 - 9 999 No. of LGAs ERP 10 000 - 49 999 No. of LGAs ERP 50 000 - 99 999 No. of LGAs ERP 100 000 - 200 000 No. of LGAs ERP > 200 000 No. of LGAs Total LGAs No. New South Wales 0 27 26 51 25 20 4 152 Victoria 0 2 8 32 12 23 2 79 Queensland 14 25 0 20 3 7 5 74 South Australia 2 23 11 25 5 4 0 70 Western Australia 37 48 11 30 6 6 1 139 Tasmania 1 5 7 13 3 0 0 29 Northern Territory 2 3 5 5 1 0 0 16 Total 56 133 68 176 55 60 11 559 1 ERP Preliminary Estimates, excluding Unincorporated ACT, Unincorporated Other Territories and other unincorporated areas. Source: Regional Population Growth, Australia (cat. no. 3218.0)

The ACT is excluded from the above table because it consists of one LGA - Unincorporated ACT. All LGAs with a population of less than 1,500 usually resident people in the 2006 Census of Population and Housing, and unincorporated areas of states and territories, have been excluded from the analysis in this article.


CENSUS COUNTS AND POPULATION ESTIMATES

All data used in this article is from the 2006 and 2011 Censuses of Population and Housing. Census data has certain limitations and some adjustments have been made to the Census counts used in this article. These are explained in more detail in the following paragraphs.
Data presented in this article are based on the concept of 'usual residence'. This refers to the place where people usually lived or intended to live for a period of six months or more in 2011. All visitors to a dwelling have been excluded, as they are counted in their own LGA of usual residence. Overseas visitors are also excluded from the usual residence data.

Data presented in this article may differ from the data in Census tables on the ABS website due to randomisation of numbers. For further information refer to Introduced Random Error. See 2901.0 - Census Dictionary, 2011.

Data from the 2011 Census has been used to calculate the growth rate of the population and population flows. Data from the 2006 Census has been used to calculate the growth rate of the population and the turnover relative to the size of each LGA.

The 2011 Census has three questions about where respondents usually live on Census night, and where the person usually lived one year and five years ago. The answers to these questions are recorded in the indicator variables: Usual Address Indicator Census night (UAICP), Usual Address One Year Ago Indicator (UAI1P) and Usual Address Five Years Ago Indicator (UAI5P). The analysis undertaken in this article could have been based upon place of residence one year ago, however five years was chosen in order to calculate population turnover and growth rates between the two Censuses. Using place of usual residence one year ago would have produced different results, such as lower turnover rates, as fewer people would move in a one year period than in a five year period. Using usual residence indicators and other variables relating to usual residence makes it possible to identify the pattern of gross and net movement of people between three dates: Census night, one year ago and five years ago. The following usual residence variables are available: Place of Usual Residence (PURP), Place of Usual Residence One Year Ago (PUR1P), Place of Usual Residence Five Years Ago (PUR5P). For more information about usual residence variables in the Census, see: Census Dictionary, 2011 (cat. no. 2901.0).


GROWTH AND TURNOVER RATES

Average annual growth rate in usual resident population between the 2006 and 2011 Census is calculated as a percentage using the formula below, where P₀ is the population at the start of the period, P_n is the population at the end of the period and n is the length of the period between P₀ and P_n in years.

[(P_n/P₀)^1/n-1] x 100

Population flow is the gross (total) movement into and out of a region. Population flow is defined as the gross movement of people into and out of the region between the 2006 and 2011 Census, expressed in the following formula:
Population Flow = Arrivals + Departures where:

• Arrivals were calculated using the series of questions on the 2011 Census form relating to where a person usually lives (on Census Night) and lived five years ago. These questions were used to determine the number of people who lived at a different usual address (to their current LGA) within Australia or lived overseas five years ago. Persons aged 0-4 years at the 2011 Census and 'not stated' addresses, where a person did not answer any component of where they lived five years ago, and people who recorded that they lived elsewhere in Australia five years ago but only partially stated their address, eg. a city, were excluded from this calculation. People who lived overseas five years ago were included.
• Departures were calculated using the series of questions on the 2006 Census form relating to where a person usually lives (on Census Night) and lived five years ago. These questions were used to determine the number of people usually resident in Australia who no longer lived in the same LGA in Australia that they lived in five years ago. Excluded were: people who recorded their address five years ago as 'undefined state' and 'undefined city' as it is impossible to identify the LGA these people were and therefore it is not possible to report if or where they have departed; persons aged 0-4 years at the 2006 Census; people who did not state their place of usual residence five years ago i.e. 'not stated'; overseas visitors; and residents temporarily overseas at the time of the 2006 Census.

Population turnover is derived by dividing the population flow by a 2006 Census count.

Population Turnover = Population Flow / Modified 2006 Census count

The modified Census count for 2006 used in the calculation of turnover excludes those persons who, at the 2011 Census, were aged 0-4 or who did not state where they lived five years ago. This is consistent with the calculation of arrivals. This modified count is different from the '2006 Census count' and which appears in the tables in this article and is used to calculate population growth.

The modified 2006 census count is: the 2006 Census count less the number of who were aged 0-4 in 2011, less the number of people who in 2011 did not state where they lived five years ago.


A NOTE OF CAUTION

The Census asks people where they usually lived five years before Census night. This information can be compared with place of usual residence on Census night to identify internal migration patterns within Australia. There are some limitations in using Census data to determine patterns of internal migration. Movements of people within Australia can only be determined for those counted in the 2011 Census and who stated a place of usual residence in Australia five years ago. People who made multiple moves between these periods would only be counted as moving once, or not at all if they returned to the same place. Additionally, 7% of the 2011 Census population aged five years and over did not state their usual residence five years ago. These people have been excluded from this analysis, and therefore the arrival and departure numbers may understate the actual number of people who moved between regions in the five year period. For more information on internal migration, see: Census of Population and Housing - Fact Sheets, Internal Migration, 2011.

The official population measure produced by the Australian Bureau of Statistics is the Estimated Resident Population. The use of Census data requires the adoption of different conceptual bases than are used to create official estimates within the ERP conceptual framework. The main conceptual differences are that the Census-based population turnover estimates in this publication exclude population subgroups which are incorporated into ERP, such as people under 5 years old at the time of the 2011 Census, residents temporarily overseas on Census night, and adjustments for the Census undercount. For more information on ERP, see: Australian Demographic Statistics (cat. no. 3101.0).

Users should have regard to these limitations when interpreting this data. For further information on the 2011 Census of Population and Housing, see the Census Data Quality Statement.