Internal migration is the movement of people from one defined area to another within a country. Information on internal migration within Australia is available from the Census.
The Census asks a series of questions relating to each person's usual address. The indicative data from these questions are recorded as the Usual Address Indicator Census Night, Usual Address One Year Ago Indicator and Usual Address Five Years Ago Indicator (UAICP, UAI1P, UAI5P).
Using the following variables, it is possible to identify the change of address of people for one year prior to the Census date, and for five years prior to the Census date:
Data collected in the Census only reflect movements which coincide with these particular points in time (i.e. one year ago and five years ago) in the intercensal period, even though there may have been multiple movements during this period.
- Place of Usual Residence (PURP)
- Place of Usual Residence One Year Ago (PUR1P)
- Place of Usual Residence Five Years Ago (PUR5P).
Household mobility indicators are also derived using this information. Note that persons temporarily absent, visitors, and households containing only visitors, are excluded from these variables. The following two indicators are available for Census data:
The data for place of usual residence are used mainly in conjunction with household mobility indicators for detailed internal migration studies.
- Household One Year Mobility Indicator (MV1D), where: all residents (aged one year or more) have changed address during the last year; or some residents have changed address during the last year; or no residents have changed address during the last year; or not stated (including households in which one or more residents did not state his/her usual residence one year ago).
- Household Five Year Mobility Indicator (MV5D), where: all residents (aged 5 years and over) have changed address during the last five years; or some residents have changed address during the last five years; or no residents have changed address in the last five years; or not stated (including households in which one or more residents did not state his/her usual residence of five years ago).
Such studies must be undertaken carefully; the points illustrated in the following cases should be noted.
Since the indicators are derived from usual residence at certain dates, only the net effects of any multiple movements between these dates can be derived. For example, John A Citizen was living in a South Australian rural area at the time of the 2001 Census. Six months later he moved to Melbourne for two years, and then to Adelaide where he was living at the time of the 2006 Census. Census data would only show the net South Australian country to city movement.
No movement is shown in the internal migration data for 'out and back' movements. For example, where a family move away from their place of usual residence to live elsewhere, then return before the end of the reference period to live at their previous address.
The ABS produces quarterly information on interstate migration in the publication Australian Demographic Statistics (cat. no. 3101.0). The data are derived from a combination of information that is acquired from the Census, and from unidentified information on interstate changes of address advised by the Health Insurance Commission.
See also Usual residence.