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3127.0 - Demography Working Paper 2001/5 - Evaluation of Administrative Data Sources for Use in Quarterly Estimation of Internal Migration Between 2001 and 2006, 2001 to 2006  
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For further information, contact Matt Berger at matthew.berger@abs.gov.au


1. INTRODUCTION

This report contains a review of possible sources for the Australian Bureau of Statistics' (ABS) internal migration estimates for the period 2001-2006. It is an update of Demography Working Paper 96/1 - Evaluation of Administrative Data Sources for Use in Quarterly Estimation of Interstate Migration Between 1996 and 2001 by Tricia Cook. The characteristics of each data source have been assessed against criteria which define ideal internal migration data characteristics and are detailed in separate sections of this report. Attachment A contains recommendations from Demography Working Paper 96/1 and subsequent follow-up action.

The ABS publishes quarterly estimates of the population for each Australian State and Territory (unless specified otherwise, for the remainder of this paper the term State refers to Australia's States and Territories). The ABS also prepares annual population estimates by Local Government Area (LGA) and Statistical Local Area (SLA). The population bases on which these estimates and projections are prepared are Australia's quinquennial Censuses of Population and Housing. Preparation of postcensal estimates at the State level have been based on component (administrative records) methods principally because of ready access to quality births, deaths and international migration data. Australia does not keep administrative records relating directly to internal population migration. Over time, the ABS has used a number of administrative data sources to estimate quarterly interstate migration, including electoral roll registrations, family allowance payments and, for 1996-2001, Health Insurance Commission (Medicare) data supplemented by Defence Force data. The quality of Australia's postcensal population estimates at the State level has principally reflected the quality of indirect estimation of interstate migration.

State population estimates are of high accuracy (the 1991-96 average absolute intercensal error at the State level was 0.4%), the exception being those for the Northern Territory which had an 1991-96 intercensal error of -2.9% The accuracy of 1996-2001 interstate migration estimates using Medicare data supplemented by Defence Force data and a new estimation model will only be known when 2001 Census results are available and the intercensal error is determined. Details of the model are contained in Demography Working Paper 99/2 - Estimating Interstate Migration, 1996 - 2001. Other information on interstate migration estimates is contained in Demographic Estimates and Projections: Concepts, Sources and Methods (ABS Catalogue No. 3228.0).


2. CONCLUSION

Medicare data remains the best administrative data source available for preparing postcensal internal migration estimates. Even though data problems exist, population coverage and timeliness in particular point to its superiority over other data sources.


3. EVALUATION CRITERIA

Data with the following characteristics are expected to provide ideal symptomatic indicators of postcensal interstate migration. The purpose in defining these ideal characteristics is to create criteria against which Medicare data and alternative data sources can be evaluated. The only change to criteria used for 1996-2001 data evaluation is to desirably seek data by the Statistical Division level or below as this would increase the possibility of direct estimation of sub-State populations.


CriteriaIdeal data characteristics

Population and coverageAll usual residents of Australia (minimum: complete subsets of usual residents e.g. persons aged 65+).
Data contentIndividual record data relating to age (date of birth, sex, date of move, origin and destination (minimum: personal details plus net interstate migration plus reference quarter indicative).
Geographic levelData at least at the State level is required. Data by the Statistical Division level or below is desirable.
TimelinessData released within one month after the end of reference quarter (minimum: four months after the end of the reference quarter.
Historical availabilityData available from 1 July 1996 to allow comparison with revised intercensal migration estimates for 1996 to 2001 (i.e. based on 2001 Census results) (minimum: data available from 1 July 2000, for comparison with 2000-01 internal migration data).
ConsistencyNo data definitional changes over time (minimum: data definitional changes which can be quantified).
Electronic captureCurrent data and past data available in ASCII format (minimum: current data available in some electronic format).


4. MEDICARE DATA

The Health insurance Commission is likely to be notified of changes of addresses through card-holder contact with a Medicare branch. This in turn can come about through:
  • patient claims (after non-bulk-billing transactions); and
  • a person seeking a replacement for a lost or stolen card; and
  • a person seeing to replace an expired card

In 1999-2000 the average person in Australia received 10.92 Medicare services. There was variation between States ranging from the Northern Territory having an average of 5.71 services to New South Wales having an average 11.75 services. With bulk billing now standard practice (73.1% of Medicare claims were bulk billed in 1999-2000), a flow through of change of address information to the HIC via patient claims is not a standard practice.

The following persons are eligible for Medicare coverage in Australia:
  • Australian citizens and permanent residents;
  • New Zealand citizens; and
  • persons who have applied for permanent residence in Australia (other requirements apply).

The Commonwealth Government has signed Reciprocal Health Care Agreements with some countries. Under these arrangements, residents of these countries are entitled to restricted Medicare access while in Australia.

Expired Cards

The Medicare Card Replacement Program is the primary method for provision of new cards upon expiry of old cards. In 1994 the Health Insurance Commission commenced an annual cycle of replacing members' cards in an effort to maintain the quality of the data in their files. Initially, all cards would be replaced in a 5 yearly cycle, meaning that approximately 20% of records would be updated each year. This program has since been changed in an attempt to even out future Medicare card production and now has a fluctuating cycle of between 5 and 7 years. As a consequence of this program, address details linked to cards that have been replaced in the previous 12 months are the most likely to be accurate.

When the Medicare Card Replacement Program is run, details of all cards that are going to expire at the end of a future month (approximately three months in advance) are extracted. These records are processed in the following steps:
  • If a Medicare card has been used for a patient claim within the last 9 months, the card is automatically replaced. The term 'patient claim' applies to situations where the patient has either claimed a benefit at a Medicare office or sent the claim by post (i.e. it does not include direct bill claims/assignments of Medicare benefits).
  • Any Medicare cards which show changes of address within the last 18 months are also replaced automatically.
  • The remaining data is compared against the Telstra Electronic White Pages. If the Health Insurance Commission is able to match the surname and address of the card holder with the White Pages, the card is automatically reissued.
  • The remainder of the cards are those where the Health Insurance Commission does not have confidence in the quality of the address data. Letters are sent to the last recorded address for these cardholders inviting them to apply for a replacement card. If no reply is received, the card expires at the set date. Thus, a card holder who changes address but fails to notify the Health Insurance Commission will eventually have a Medicare card that has expired.

If a card expires and is not replaced (due to a change of address as noted above) it becomes increasingly difficult for the card holder to receive medical services. For example, an expired card triggers a warning at doctors' surgeries and other providers of medical services. This applies equally to practitioners who bulk-bill their patients. In addition to the warning, medical practitioners may have the Medicare claim from an expired card refused. Therefore provision of medical services to the holder of an expired cards becomes increasingly difficult and costly to the card holder. Further, since July 2001, a current Medicare card is required for provision of government subsidised pharmaceuticals. These mechanisms encourage Medicare card holders to contact the Health Insurance Commission to renew their card, and subsequently provide new address information. Where more than one person is on the same card this will increase the probability of change in address information being advised to the Health Insurance Commission.

Although the Medicare Card Replacement Program may invite a card holder to apply for a replacement card, it is only through a card-holder approaching a Medicare branch that address information may be updated. It is now possible for a branch to be approached in person, via a telephone, or in writing.

EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), Medicare Data

CriteriaEvaluation

Population and coverageIn theory the Medicare population base is all Australian usual residents plus non-Australian residents granted temporary registration. In practice a variety of Australian usual residents who are eligible to use Medicare are unlikely to do so consistently because of access to alternative health services (for example Indigenous persons, defence force personnel, prisoners and persons eligible for Department of Veteran's Affairs Health Services). Conversely Medicare's population base is expected to exceed the ideal population base (i.e. all Australian usual residents) with regard to registrations relating to international visitors and former Australian usual residents who have died or are now permanently resident overseas but have not as yet been deleted from the register.

The Health Insurance Commission anticipate coverage of children by the Medicare register, especially the recently born and toddlers, has been further enhanced by the introduction of the National Childhood Immunisation Register in January 1996. The National Child Immunisation Register is administered by the Health Insurance Commission as a subset of the Medicare register.
Data contentMedicare data meets this criterion.
Geographic levelMedicare data meets this criterion. Address data in the Medicare file is based on Australia Post postcodes, which can be converted to SLAs using a concordance.
TimelinessMedicare data meets this criterion.
Historical availabilityMedicare data meets this criterion.
ConsistencyThere have been some inconsistencies in the 1990s related to Medicare's card re-issue schemes.
Electronic captureThe data is available in electronic form.

(a) Refer Section 2.

Recommendations

Medicare remains a viable source of data.


5. TAXATION DATA

Change of address details from Personal Income Tax files are currently used by Statistics Canada and the US Census Bureau to produce annual estimates of internal migration. This data source can not be used to produce quarterly estimates of internal migration as data is only available annually. Statistics Canada uses taxation derived annual estimates of interprovincial migration in preference to quarterly estimates of interprovincial migration prepared from child endowment style data. Taxation data is valued for its estimation of migration relating to persons aged 15 to 65 years in particular. Statistics Canada commenced using taxation data in 1976, at a time when their child endowment data gave 100 per cent coverage of address details relating to children aged under 18 years, and despite the inability of annual taxation data to estimate multiple migration within a year.

The ABS undertook an extensive evaluation of taxation data as part of research into alternative administrative data sources in 1990. A number of limitations associated with taxation data were identified from this 1990 research and many were consistent with limitations reported by Statistics Canada and the US Census Bureau. The principal limitation was lack of data timeliness. Specifically, data would not become available from the ATO until 10 months after capture. Consequently the reference period of interstate migration estimates would be lagged by more than one year.

Recent discussions with the ATO focused on identifying any changes in collection or policy practises which may have altered the 1990 findings. In summary, whilst a number of changes have occurred since then, the principal result is that access to taxation data will be even less timely although data is electronically captured for more Australian taxpayers than in 1990.

EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), Taxation Data

CriteriaEvaluation

Population and coverageThe population available to be covered from personal income tax records is all persons who submit tax returns to the Australian government in two consecutive years and their identified spouses/partners. Dependant child details are not captured on tax returns but estimates of numbers of dependant children may be possible from rebate details. This population base differs from the ideal population base (i.e. all Australian usual residents) for those Australian usual residents who do not submit income tax returns in two consecutive years and for those persons who submit returns but are not usual Australian residents. In particular, coverage for persons aged over 65 years tends to be particularly inconsistent.
Data contentData entry policy changes and the introduction of direct electronic lodgement since 1990 have resulted in the ATO maintaining details on all submitted returns not just those considered 'taxable'. Individual returns (tax-pack forms) are required to be lodged by October of the referenced financial year unless submitted via an agent. Agent submitted returns are not required to be lodged until March of the year following the reference year. In 1997/98, agent submitted returns accounted for 75 per cent of all (9.8 million) returns.
Geographic levelGeographic level of required details can be captured direct from postcode. This assumes that the addresses of people who submit tax returns are available rather than only the addresses of accountants and tax agents.
TimelinessTo ensure unimpeded processing of returns, the ATO prohibits use of their databases for non-tax purposes until 12 months after the reference financial year. This means the reference period of interstate migration estimates would be lagged well in excess of one year.
Historical availabilityTaxation data meets this criterion.
ConsistencyTaxation data meets this criterion.
Electronic captureTaxation data meets this criterion.

(a) Refer Section 2.

The captured data is expected to meet ideal data content requirements except that movements will not referenced to specific quarters in a survey year. Taxation data is also expected to be able to meet ideal historical and data consistency requirements.

Recommendations

Taxation data is unsuitable for use in quarterly estimation of interstate migration because it is collected annually. Its potential for validating or augmenting quarterly estimates is impaired by timeliness issues and problems associated with comparing quarterly estimates and annual estimates of migration because of multiple migration within a year.


6. FINANCIAL INSTITUTIONS DATA

Investigations into the likelihood of sourcing quality change of address data from financial institutions commenced with discussions with officers from ABS Finance Section. As Finance Section was due to start a series of formal consultations with Australia's major banks, it was hoped preliminary details about problems the major banks envisages in supplying change of residential address data could be sought on Demography's behalf. During the May 1996 consultations, Finance Section officers decided against pursuing such information because of the undue burden such discussions would add to meetings that were already extremely demanding. The principal purpose of these consultations was to advance data requirement changes which had not been well received when first proposed at a Bankers Association meeting held in Sydney on 13 March 1996.

To be of value in estimating interstate migration, it is anticipated financial institutions will need to provide selected data relating to bank accounts in which a residential address change occurred during the reference quarter. Bank account holdings rather than credit card holdings are expected to cover a greater proportion of the Australian usual resident population since segments of the population (e.g. low income earners, children etc.) are expected to be ineligible for credit card accounts. Details on name, age (date of birth), sex, old residential postcode and new residential postcode will be required. Name data is considered necessary because of the possibility of persons having an account with more than one financial institution or having more than one account with one institution.

If undertaken, extraction of migration information from financial institution data is expected to require the development and maintenance of an extensive database. Record matching will be required to avoid the possibility of double (multiple) counting occurring as a result of persons having a bank account with more than one financial institution. The success of detecting replicated address changes will depend, amongst other factors, on customers notifying more than one institution of an address change during the same quarter and that each institution processes this information during the same quarter.

EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), Financial Institutions Data

CriteriaEvaluation

Population and coverageData relating to bank account holdings are expected to be greater than the ideal population base (i.e. all Australian usual residents) as non-Australian usual residents are also expected to have bank accounts in Australia. This creates a problem because there is a 'one to many' relationship of accounts to customers. Any system has to be able to accurately derive the number of people from the number of accounts.
Data contentAddress details may allow accounts held by persons usually resident overseas to be identified and excluded from coverage. Data relating to name, age, sex, old residential postcode and new residential postcode are expected to meet data content requirements. Data may not be readily available from some banks because of operational size considerations and or deliberate regionalisation policies.
Geographic levelPostcode level data allows for sufficient geographic information
TimelinessFinancial institutions data could meet this criterion, although whether this can be guaranteed is unknown at this time
Historical availabilityOnly possible for 2006.
ConsistencyUnknown.
Electronic captureData would be able to be captured electronically.

(a) Refer Section 2.

Recommendations

Preliminary discussions with ABS officers working with the financial sector indicate this sector currently finds ABS data demands extremely burdensome. Furthermore there is some contention as to whether all financial institutions would be able to provide national change of address data.

While financial institutions may capture data which would assist with interstate migration estimation, it is expected to be unduly expensive in terms of reporting load considerations and data storage and processing costs, to obtain and extract the necessary information.


7. FINANCIAL INSTITUTIONS ADDRESS REDIRECTION SERVICE DATA

A new service offers a complete redirection service to people who change address. A consortium of financial institutions run the service for their customers. It aims to supplant Australia Post's mail redirection service. Initial estimates by those starting up the database are that 30 to 40% of households who move will use this service.

EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), Financial Institutions Address Redirection Service Data

CriteriaEvaluation

Population and coverageCoverage is limited to customers of financial institutions who choose to use this service. It is highly unlikely that this criterion would be able to be met by the scheme.
Data contentData is kept at the household level although ABS can request additional data items. It is highly unlikely that sex and date of birth for all individuals in a household could be reliably collected under this scheme.
Geographic levelPostcode level data allows for sufficient geographic information
TimelinessThe database could be interrogated at any time so movement data could be available at any interval, enabling this criterion to be met.
Historical availabilityThis criterion could not be met until 2006.
ConsistencyIt is quite likely that this criterion could be met.
Electronic captureData could easily be made available in electronic form.

(a) Refer Section 2.

Recommendations

Given that coverage of the population is unknown, and that age-sex information will not be available, financial institutions address redirection service data should not be pursued further at this point.


8. AUSTRALIA POST DATA

In addition to maintaining a database on national residential delivery points (i.e. house and unit addresses), Australia Post operates a commercial address change service. Details relating to permanent address changes are held on an address change database. The database captures old and new address details along with the name/s of the household member/s whose mail is to be redirected from this address.

Australia Post believe their address change facility is currently used by about 70 per cent of households which move within Australia (i.e. either intrastate or interstate). The data comparisons below suggest these household estimates translate to approximately 45 per cent of persons who move interstate. Substantial regional variations in usage of this facility are apparent even at State level.

COMPARISON OF ESTIMATED INTERSTATE MIGRATION DATA WITH AUSTRALIA POST DATA, by States and Territories of Arrival and Departure, September Quarter 1995

Arrivals
Departures
Australia Post (a)
Estimated Interstate Migration (b)
Difference
Australia Post (a)
Estimated Interstate Migration (b)
Difference
State/Territory
No.
No.
%
No.
No.
%

NSW
9,366
20,145
46.5
8,903
22,833
39.0
VIC
6,322
12,519
50.5
7,005
17,470
40.1
QLD
10,296
25,818
39.9
7,967
16,018
49.7
SA
2,788
5,376
51.9
3,721
7,533
49.4
WA
3,528
7,528
46.9
3,701
6,456
57.3
TAS
1,113
2,447
45.5
1,052
3,102
33.9
NT
1,470
3,793
38.8
2,337
4,055
57.6
ACT
1,788
3,851
46.4
1,985
4,010
49.5
AUST
36,671
81,477
45.0
36,671
81,477
45.0

(a) Source: Australia Post, estimate of persons who moved within Australia during September Quarter 1995 based on change of address data.
(b) Source: Australian Demographic Statistics, September Quarter 1995, Cat. No: 3101.0, estimate of persons who moved within Australia during September Quarter 1995 based on Medicare data, preliminary estimates.


EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), Australia Post Data

CriteriaEvaluation

Population and coverageThe population base of Australia Post's Change of Address database is all persons (usual resident of Australia or otherwise) with an active permanent redirection notice and others who are nominated on these notices. It is difficult to assess how well this population base meets the ideal population base (i.e. all Australian usual residents). An evaluation of Australia Post data in 1994 suggests service usage is inversely related to distance moved. Definitely, since overseas redirections are not provided by this service, it appears unlikely that emigrants or overseas visitors would use it unless looking to redirect mail to another Australian address for subsequent private redirection overseas. However, there are a number of other possible factors which may also influence service usage. For example, income, intended duration of migration and whether or not all household members will be involved in the move. In addition, age and or English literacy skill may dictate which household members are nominated on redirection forms. In essence, Australia Post's change of address population base is unlikely to be a random sample of Australia's usual residents. Consequently, unless specific characteristics can be identified from within the Australia Post change of address population base, unbiased estimates of interstate migration are not possible from this data source.
Data contentThe absence of age details is a significant data deficiency. Furthermore, Australia Post reference dates will relate to the date the redirection notice becomes active and this date may or may not coincide with date of migration. For example, variations in arrival and departure rates (refer table above) may reflect significant regional differences in submission lead/lag times (refer NT and Qld). Since submission of change of address notifications depends on knowing a destination address, variability can be expected because of factors such as differences in regional housing vacancies and access to temporary accommodation arrangements (e.g. staying with friends or family). An assessment of submission lead/lag times is needed before Australia Post reference date data can be used with confidence.
Geographic levelPostcode level data allows for sufficient geographic information
TimelinessAustralia Post change of address data is expected to meet this criterion.
Historical availabilityAustralia Post change of address data is expected to meet this criterion.
ConsistencyAustralia Post change of address data is expected to meet this criterion.
Electronic captureData would be able to be captured electronically.

(a) Refer Section 2.

Recommendations

In theory, Australia Post change of address data has considerable potential to assist interstate migration estimation. Current lack of information about the characteristics of users of this address change service prevent this data source from being able to be used to prepare unbiased estimates of interstate migration. Consequently, at present Australia Post change of address data is not considered a good alternative administrative data source to Medicare data.

Before it could be used, details about the propensity for Australia's usual residents to use Australia Post's change of address services is required. Investigations would need to identify the characteristics of direct users and indirect users (i.e. other nominated household members) and submission practices in relation to date of migration.

Although now dated and restricted to only two Queensland LGAs, the result of the 1994 analysis of Australia Post data indicates a potential for change of address data to assist with sub-State population distribution.


9. TELEPHONE CONNECTIONS DATA

At present, telephone connections data is a household based administrative data collection. While this does not prevent the data source from being used to estimate interstate migration, it would require substantive changes to be made to the estimation methodology presently used by the ABS. Furthermore, although telephone connection is extensive, Telstra is unable to assure change of address details except for phone transfers (i.e. short distance migrations). Thus telephone connections data is not presently recommended as an alternative to Medicare data or even as a data source to augment Medicare data.

New carriers continue to enter the market place. While each carrier maintains a database of customer information, this data flows into the Integrated Public Number Database (IPND) which is jointly administered by the Australian Communications Authority and Telstra. The IPND is designed to assist emergency services in carrying out their functions. This central database is household based, containing name and address for each phone number in Australia.

EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), Telephone Connections Data

CriteriaEvaluation

Population and coverageAs telephone connections data is a household based collection, this poses difficulties in accurately deriving numbers of individuals.
Data contentSex and date of birth are not recorded on the database. It does not meet this criterion.
Geographic levelPostcode level data allows for sufficient geographic information
TimelinessThe database could be interrogated at quarterly intervals.
Historical availabilityThis criterion could be met for 2006.
ConsistencyThere have been a number of policy shifts and market forces which have caused definitional inconsistencies in recent times. This criterion is not met.
Electronic captureThe data is available in electronic form.

(a) Refer Section 2.

Recommendations

The many to many relationship between phone numbers and persons mean that telephone administrative data is unlikely to be a good source of internal migration data.


10. SOCIAL SECURITY DATA

All social security payments are subject to means testing (i.e. income and assets tested, with some assets considered to have income potential according to deeming rules) of individuals as well as their spouses/partners. At present, most immigrants are required to wait 2 years before becoming eligible for social security payments (except Family Allowance payments). Details specific to Unemployment, Family Allowance and Age Pension data are provided separately below.

Unemployment Data

With regard to unemployment data, recipients are required to lodge declarations fortnightly. Consequently residential address data is potentially current within a two week time frame. The reliability of this address data is expected to have declined since unemployment allowances began being paid directly into bank accounts rather than being posted to recipients. Change of address data is not specifically captured by the unemployment database but it is expected to be available by comparison of database snapshots at different points in time. Population coverage issues are expected to limit the value of unemployment data. Means tests prevent all unemployed persons from being eligible to receive benefits while some low income employed persons are eligible for partial payments. As a consequence, it will be difficult to find appropriate benchmarks against which unemployment transfers data can be weighted to produce estimates of internal migration. To further exacerbate this issue, migration amongst the unemployed is unlikely to reflect general migration patterns.

Family Allowance Data

The Department of Family and Community Services (DFACS) holds details about the number of children eligible for benefit. Change of address details are not expected to be updated more frequently than annually as payment of Family Allowances is made directly and electronically into bank accounts. Payments are assessed against the previous year's taxable income. Such details are requested each year before payments continue. It is expected change of address data could be obtained by comparing separate snapshots of this file at different points in time.

An examination of Family Allowance data revealed the number of recipients had declined significantly over the past five years. The following is a listing of policy changes to Family Allowance eligibility since 1985, which are expected to have impacted on data comparability over this period.


Year
Change to Family Allowance eligibility

1985
Dependent children aged 18-24 years excluded from Basic Family payment (extended to exclude dependent children aged 18-24 of pension recipients in 1990).
1987
Children who have never lived in Australia excluded from all Family payments.
1987
Introduction of Income test for all Family payments.
1989
Children who have lived overseas for 3 or more years excluded from all Family payments.
1992
Introduction of Assets tests for Basic Family payment.
1994
Introduction of Income and Assets tests for all Family payments, including deeming rules in relation to specific assets.
1995
Expansion of Income and Assets tests to treat taxable income deductions for negatively geared properties as income. Parenting allowance introduced.
1996
Single Family Payment introduced.
1998
Change of name from Family Payment to Family Allowance.
2000
Family payments moved under a different act as part of the move to a new taxation system (1 July).


Age Pension Data

Eligibility for an age pension allowance is subject to means testing of the individual and the spouse. Change of address details are not expected to be updated more frequently than annually as payment of Age Pension Allowances is made directly into bank accounts.

An extensive assessment of age pension data and its value in estimating interstate migration for persons aged 60 years and over was undertaken as part of investigations into alternative data sources to Medicare in 1990. The summary conclusion from this investigation was that whilst age pension transfers would probably be adequate to estimate the total number of interstate movers for Australia as a whole in the 60 plus age range, coverage would be insufficient to estimate net interstate gains or losses for individual States and Territories.

EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), Social Security Data

CriteriaEvaluation

Population and coverageChanging eligibility requirements for the above forms of social security payment mean that the population base changes frequently. Coverage therefore falls short of ideal requirements.
Data contentThe key data items are collected. The data would most likely meet this criterion.
Geographic levelPostcode level data allows for sufficient geographic information
TimelinessThe database could be interrogated at quarterly intervals.
Historical availabilityThis criterion could be met for 2006.
ConsistencyFrequent policy changes over the last 15 years have caused many inconsistencies in the data. This criterion could not be met.
Electronic captureThe data is available in electronic form.

(a) Refer Section 2.

As a consequence of the eligibility conditions which apply to all social security payments, the population bases associated with the types of social security data outline above are less than the ideal population base (i.e. all Australian usual residents). The introduction of significant policy changes to eligibility conditions, especially with regard to Family Allowance Payments, in the past have impaired the historical consistency of these datasets. Notification of address changes are required only annually for Age Pension and Family Allowance payments and in general, payment by direct electronic transfer, limits the ability of social security data to be used with confidence to estimate internal migration within Australia. Past and expected changes to social security eligibilities are expected to impair data consistency. Social security data is expected to meet ideal data criteria with regard to time-lags and electronic availability.

Recommendations

Changes (both past and expected) to social security allowance policies limit population coverage of associated payment datasets and have impaired their historically comparability. Furthermore population coverage limitations associated with these datasets are more extensive than Medicare. In addition, since address details of Age Pension and Family Allowance recipients are updated annually, these datasets can not be used in quarterly estimation of interstate migration. Consequently, social security data is not considered a viable replacement for Medicare data at present.


11. SCHOOL ENROLMENT DATA

A comprehensive assessment of school enrolment data for use in estimation of interstate migration was undertaken by the ABS as part of investigations into alternative administrative data sources to Medicare in 1990. The conclusion was that interstate migration data were not available for school students and could not be derived from existing administrative records at the State or national level. However, the data were generally captured (though not necessarily in the required format) by schools for new enrolments and could conceivably be collected for all enrolments and collated as part of the National Schools Statistics Collection (NSSC), results of which are published by the ABS. As at August 2000, there has been no substantive change to this situation.

Data comparisons undertaken during the research in 1990 revealed a high correlation between head counts and ERP at 30 June. This suggested the potential for developing estimates of interstate migration for children aged 6 to 14 years from school enrolment data. However for this potential to be exploited, a major change to how the data is collected would need to occur.

EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), School Enrolment Data

CriteriaEvaluation

Population and coverageThe school population does not cover the population at all ages, but is very close to being a full subset (ie persons aged 6 to 14 years) since schooling is compulsory up until age 15 in most states and at least age 14 in all states.
Data contentAlthough some data is collected down to the school level, ABS only receives aggregated data which is not in a format which could be used. The data does contain student's ages by grade by state but this is not sufficient to estimate internal migration.
Geographic levelPostcode level data allows for sufficient geographic information. As noted above, however, this is only at the school level at best, which restricts usefulness.
TimelinessThe data is available annually on 4th August for the previous calendar year reference period.
Historical availabilityAggregated data is available subject to the lag mentioned under 'timeliness'.
ConsistencyUnknown.
Electronic captureData is currently supplied in spreadsheet form.

(a) Refer Section 2.

Recommendations

Comprehensive data relating to student transfers may be kept by schools but such data are not collected as part of the annual NSSC. As such, this is not a viable data source for estimating internal migration.


12. DRIVERS LICENCE DATA

In 1999 and 2000, ABS investigated the possibility of using interstate transfer data from the new national drivers licence registration system. The system, called NEVDIS, is a national repository for drivers licence data, accessible from all states. Data useful to ABS includes date of birth, date of change of address, new address. Tasmania and ACT will be the last to adopt NEVDIS for licensing in March and July 2001 respectively.

The main limitation of the NEVDIS system is the fact that is does not record a previous address, only the current address. Thus it fails the Data Content criterion for address of origin. ABS requires both a 'to' and 'from' address to be of use in estimating interstate migration. There are currently no plans to include a 'from' address on NEVDIS. Other shortfall against the criteria is the fact that not all usual residents of Australia hold drivers licences, and that not all states will be on-line by the July 2000 cutoff for Census comparability.

EVALUATION AGAINST IDEAL INTERNAL MIGRATION DATA CRITERIA(a), Drivers Licence Data

CriteriaEvaluation

Population and coverageThis is less than ideal as only the licensed driving population is covered. In all states this is only this aged 18 and over for a full licence and 17 and over for a provisional licence.
Data contentThe limitation here is that a 'from' address is not available, that is to say the system only contains the latest address. This prevents it being used to estimate interstate migration.
Geographic levelPostcode level data allows for sufficient geographic information
TimelinessTimeliness is acceptable because data could be captured at quarterly intervals.
Historical availabilityThe data fails this criterion because not all States (as at mid 2000) are on-line yet.
ConsistencyIt is too early to assess data against this criterion as the system is not yet fully functional.
Electronic captureThe data could be captured in electronic format.

(a) Refer Section 2.

Recommendations

Drivers licence data is not able to be used as a data source. If at some point in the future NEVDIS is enhanced to include a 'from' address, it would be worth exploring this option further.


13. OTHER ADMINISTRATIVE DATA

A number of other commonly used datasets were excluded from this investigation. The excluded datasets included electricity connections, residential building permit applications, electoral roll registrations and motor vehicle registrations. The decision to exclude these other data sources was based on the results of previous investigations by the ABS or other international organisations. In general, past investigations revealed criteria deficiencies which exceed those associated with Medicare data and which were considered unlikely to have altered significantly since last evaluated. For example, electricity connections transfers data is not available nationally and connections data (like building permit data) is subject to fluctuations in the building industry as well as population change. Similarly, past research, most recently in New Zealand and Canada, reconfirms motor vehicle registrations data (like electoral roll data) is problematic because of timeliness considerations. This is despite the legal requirement for people to notify authorities of address changes within a fixed time period following migration. These conclusions do not necessarily limit the value of these datasets in sub-State population estimation but such evaluations are outside the scope of this paper.


Demography Program
September 2001


ATTACHMENT A

This attachment summarises the response to recommendations from the August 1996 ABS Demography Working Paper 96/1 - Evaluation of Administrative Data Sources for Use in Quarterly Estimation of Interstate Migration Between 1996 and 2001.

RECOMMENDATIONS FROM DEMOGRAPHY WORKING PAPER 96/1 AND SUBSEQUENT RESPONSES/FOLLOW-UP ACTIONS

RecommendationResponse/follow-up action

MEDICARE DATA

1. ABS develop a closer working relationship with the Health Insurance Commission (HIC)Quarterly meetings between ABS and the HIC are held.
2. The HIC is encouraged to statistically verify why numbers of Medicare registrants grew at approximately twice the annual number experienced prior to the card reissuance program in 1991.The HIC has advised that the numbers of persons enrolled with Medicare grew at twice the rate after 1992 when compared with the growth from 1990 to 1992. There may be a number of factors which contribute to the increased growth but the cancellation of enrolments in 1992 as shown by the decline from 1992 to 1993 involved the cancellation of eligible persons who had not used Medicare for some time. These eligible persons may have subsequently re-enrolled after 1993, exaggerating the normal growth. The difference between the 1990 and 1995 numbers is quite reasonable showing a growth of 0.7 million over the 5 years.
3. The Health Insurance Commission is encouraged to obtain deaths data from each State and Territory Registrar to update the Medicare register. The Medicare register is currently being updated using deaths data from only some State Registrars because of data access cost considerations.Deaths registered in all States are now used to update the Medicare register.
4. A comparison of age related intercensal discrepancy data or 1996 Census interstate migration data be undertaken to reveal the potential benefit of augmenting Medicare data with alternative age-specific data sets.A comparison was undertaken as part of the background work associated with Demography Working Paper 99/2 - Estimating Interstate Migration, 1996 - 2001. The major problems were associated with males aged between 16 and 29 inclusive and females aged between 18 and 24 inclusive for which satisfactory alternative data sources did not exist in 1996.
5. An evaluation of the impact of short-term (visitor) transfers be undertaken with the objective of assessing whether such data should be excluded from Medicare transfers data used in interstate migration estimation in the future.No investigation of the impact of short-term visitor transfers has yet been undertaken. However, visitors to Australia on reciprocal arrangements are now identified in Medicare data and are removed from internal migration estimates.
6. The existence of linked child adult records offers the potential for a closer examination of child/parent migration patterns following adult separation.The HIC has advised that it is important to understand that while a family can be grouped on a Medicare card, so can any group of persons residing together. Conversely, persons in a family can choose to have separate cards (e.g. parents can be on separate cards with their children registered on each card). Children regularly cared for by a neighbour or relative can be included on the carer's card. Children can also be included on different cards under different names, although the PIN number remains the same. Medicare's prime purpose is to list eligible persons and ensure that claims for Medicare benefit are promptly and accurately paid. Claims processing tasks do not require any adult/child link, merely that each eligible person be identified. Allowing groupings of persons on the same card and various policies in respect of children is done to accommodate clients' wishes.

MONTHLY POPULATION SURVEY (LABOUR FORCE) DATA

7. The Monthly Population Survey estimates can not currently be relied upon to validate annual estimates of interstate migration. The ABS is investigating what changes would be needed to allow reliable estimates of interstate migration to be produced from the Monthly Population Survey. If the required sample design or processing changes are impracticable, it is recommended that collection of internal migration data from the Monthly Population Survey be discontinued.The Monthly Population Survey does not provide a satisfactory basis on which to estimate interstate migration. Investigations did not suggest any problem with either the sample design or estimation method. Differences with Medicare based estimates can be attributed to conceptual and measurement issues and to the variability associated with the estimation of small populations. Interstate migration involves about 2% of the Australian population in any one year and hence on average 0.5% in any quarter (Population Growth and Distribution, Australia, 1996 (ABS Cat. no. 2035.0), table 3.1). State level flows by age and sex are components of this 0.5% and hence even more problematic.

TAXATION DATA

8. Taxation data is unsuitable for use in quarterly estimation of internal migration because it is collected annually. Its potential for validating or augmenting quarterly estimates is impaired by timeliness issues and problems associated with comparing multiple migrations within a year. However since international experiences indicate taxation data is a good source for estimating internal migration involving persons aged 15 to 65 years, it is recommended that a comparison of age related interstate migration from the 1996 Census be undertaken to reveal the potential benefit of augmenting Medicare data with age-specific data sets. If the results of this analysis are positive, it is recommended discussions be held with the ATO regarding the possibility of improving timely access to taxation data.Income tax data could have a role in the revision process. While discussion with the ATO has occurred, the major changes to the taxation system in 1999-2000 makes it a data source undergoing major change and hence it is not in a position to provide a consistent basis for future estimation. It is not intended to pursue this option unless the review of 1996-2001 estimates indicates major problems with Medicare data.

FINANCIAL INSTITUTIONS DATA

9. Whilst financial institutions may capture data which would assist with interstate migration estimation, it is expected to be unduly expensive in terms of reporting load considerations and data storage and processing costs, to obtain and extract the necessary information. Consequently, it is recommended financial institutions data not be pursued at this point.No further action.

AUSTRALIA POST DATA

10. The current lack of information about the characteristics of users of Australia Post's change of address service prevent this data source from being used to prepare unbiased estimates of interstate migration. Details about the propensity for Australia's usual residents to use Australia Post's change of address services is required. Investigations will need to identify the characteristics of direct users and indirect users (i.e. other nominated household members). Details about submission practices in relation to date of migration also need to be determined. It is recommended the ABS encourage Australia Post to undertake these investigations for their own benefit.No further action.

TELEPHONE CONNECTIONS DATA

11. The introduction of personal phone numbers is expected to require significant changes to telephone administrative data. Details on changes to billing addresses for portable personal phone numbers are expected to offer an excellent potential source of internal migration data. It is recommended the ABS initiate high level discussions with Telstra and Optus with a view to negotiating quarterly access to these future data sources.Initial contact made with Telstra. The subsequent fragmentation of telephone services makes such sources of data problematic for estimation of interstate migration.

SOCIAL SECURITY DATA

12. Changes (both past and expected) to Social Security Allowance policies limit population coverage of associated payment datasets and have impaired their historical comparability. Furthermore population coverage limitations associated with these datasets are more extensive than Medicare. In addition, since address datasets are updated annually, these datasets can not be used in quarterly estimation of interstate migration. Consequently, it is recommended Social Security data not be considered a viable replacement for Medicare data at present.No further action.

SCHOOL ENROLMENT DATA

13. Recent discussions with ABS personnel indicate that comprehensive data relating to student transfers may be kept by schools but such data are not collected as part of the annual NSSC. In addition, school censuses are conducted more frequently than annually by the States and Territories. Consequently, it is recommended State and Territory Education departments be encouraged to capture change of address details as school enrolment transfers data offer great potential as a validating data source of interstate migration for children aged 6 to 14 years. In addition, such data are expected to assist research into student retention rates.Contact in 1996 and 2000 with the Secretariat of the Ministerial Council on Education, Employment, Training and Youth Affairs indicates that capturing change of address data is not a viable proposal.



BIBLIOGRAPHY

Australia Post 1995, Customer List Interface Subscriber Guide, Address Post: Version 1.6

Demography Working Paper 96/1 - Evaluation of Administrative Data Sources for Use in Quarterly Estimation of Interstate Migration Between 1996 and 2001

Department of Family and Community Services 1998 (A Addai & K Chan), Changing Composition of the Family Allowance Population 1993-199l, AIFS Conference Paper.

Statistics New Zealand 1998, Adjustment of Post-Censal Population Estimates for Census Undercount, Research Report #3,

Steel, D. and Harrington, P 1996, 'Quality Issues in Telephone Surveys: Coverage, Non-response and Quota Sampling', Australian Journal of Statistics, vol. 38, no. 1, pp.15-34.


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