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4130.0.55.001 - Housing Occupancy and Costs, Australia, 2005-06  
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 31/10/2007   
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EXPLANATORY NOTES


INTRODUCTION

1 This publication presents the housing costs and characteristics of households and persons resident in private dwellings in Australia, compiled from the 2005-06 and earlier Surveys of Income and Housing (SIH). The survey collected information on sources of income, amounts received, housing costs and characteristics of persons aged 15 years and over. Households in very remote areas are excluded.


2 The Information Paper: Survey of Income and Housing, User Guide, Australia, 2005-06 (cat. no. 6553.0) is available to assist users evaluate and interpret results from this survey.


3 The SIH was conducted continuously from 1994-95 to 1997-98, and then in 1999-2000, 2000-01, 2002-03, 2003-04 and 2005-06. The 2005-06 SIH collected information from a sample of approximately 10,000 households over the period July 2005 to June 2006. Future cycles of the SIH will be conducted every two years.


4 Other collections conducted by the Australian Bureau of Statistics (ABS) which cover housing are:

  • Census of Population and Housing, 2006
  • General Social Survey, 2006
  • Australian Housing Survey, 1994 and 1999

5 Collections conducted by the ABS which cover housing for Indigenous Australians are:
  • Community Housing and Infrastructure Needs Survey, 1999, 2001 and 2006
  • National Aboriginal and Torres Strait Islander Social Survey, 2002.

6 Care should be taken when comparing data from the different sources due to the different methodologies used in these surveys.



Changes in this issue

7 The 2005-06 SIH was conducted as a stand alone survey, whereas the 2003-04 SIH was integrated with the Household Expenditure Survey (HES). This may have had an impact on response bias. The HES and SIH will be integrated each time the HES is run, with the next HES scheduled for 2009-10.


8 The 2005-06 SIH survey content was largely a repeat of that used in the 2003-04 SIH, with some minor wording changes.


9 Changes in this issue are:

  • the housing cost estimates for 2003-04 and 2005-06 now include information on housing costs for tenure types other than owners and renters (such as rent-buy and shared equity arrangements), which were first collected in the 2003-04 survey. In prior issues of this publication housing costs comprised: rates payments for owners; rates and housing loan payments for owners with a mortgage; and rent payments for renters. The housing costs measure is no longer dependent on tenure - it is defined as the sum of rent payments, rates payments, and mortgage or unsecured loan payments if the initial purpose was primarily to buy, add or alter the dwelling. The 2003-04 housing cost estimates in this issue have been revised accordingly. The revised definition adds about $1 (less than 1%) to mean weekly housing costs.
  • additional tables for each state and territory have been included in the data cube released in association with this publication. These tables show information on housing costs, housing costs as a proportion of gross income and selected household characteristics from the years 1994-95 to 2005-06.
  • the inclusion of all salary sacrificed amounts in income estimates for 2003-04 and 2005-06. In previous issues estimates have included only some salary sacrificed amounts. For more information see Appendix 4 of Household Income and Income Distribution, Australia, 2005-06 (cat.no.6523.0).
  • households with nil or negative income have been excluded from calculations of housing costs as a proportion of gross income. These households make up 0.5% of all households.
  • the use of more detailed age benchmarks when determining the weights to be allocated to each household in the 2005-06 estimates. For further information refer to paragraph 63 of the Explanatory Notes.
  • expanded detail for age groups, splitting a category for those aged 65 years and over into two categories for 65-74 years and 75 years and over.
  • the inclusion of gross weekly household income estimates in Table 1.


CONCEPTS AND DEFINITIONS

10 The concepts and definitions relating to statistics of housing costs are described in the following section. Other definitions are included in the Glossary.



Household

11 The household is the basic unit of analysis in this publication. A household consists of one or more persons, at least one of whom is at least 15 years of age, usually resident in the same private dwelling. The persons in a household may or may not be related. They must live wholly within one dwelling.


12 The household is adopted as the basic unit of analysis because it is assumed that sharing of the use of goods and services occurs at this level. If smaller units, say persons, are adopted, then it is difficult to know how to attribute to individual household members the use of shared items such as food, accommodation and household goods. Intra-household transfers, however, are excluded. For example, if one member of the household were to pay board to another member of the same household then this is not considered as an increase in the amount of income or housing costs of the household. If such transfers were to be included there would be double counting.



Housing costs

13 Housing costs are the recurrent outlays by household members in providing for their shelter. The data collected on housing outlays in the SIH are limited to major cash outlays on housing, that is, mortgage repayments, rates (general and water) and rent payments. Mortgage, rent and rate payments are shown in this publication as weekly equivalents.


14 Only payments which relate to the dwelling occupied by the household at the time of interview, that is, a respondent's usual place of residence, are included. Housing costs only include mortgage/loan payments if the purpose of the loan at the time it was initially taken out was primarily to buy, build, add to or alter the occupied dwelling.


15 There are a number of limitations to the housing costs information obtained in the SIH, due to practical data collection considerations. These limitations should be especially borne in mind when comparing the housing costs of different tenure and landlord types, that is, when comparing the costs of owner occupiers with the costs of renting households, and when comparing the costs of households renting from state and territory housing authorities with the costs of other renters.

  • Households are sometimes reimbursed some or all of their housing costs, but these reimbursements have not been separately collected in the SIH. Commonwealth Rent Assistance (CRA), paid by the Australian Government to qualifying recipients of income support payments and family tax benefit, is the most important type of reimbursement of relevance to these statistics. If rent assistance receipts were subtracted from gross housing costs, it has been estimated that the housing costs of households receiving rent assistance would be about 30% lower on average, and the housing costs of all households renting from landlords other than the state/territory authorities would be about 10% lower on average.
  • Mortgage repayments made by owners with a mortgage include both the interest component and the principal or capital component. For many purposes it is more appropriate to consider repayments of principal as a form of saving rather than as a recurrent housing cost. It reflects the purchase of a housing asset by increasing the equity in the property held by the household and is an addition to the wealth of the occupants. The 2005-06 SIH indicated that about 35% of the housing costs of owners with a mortgage comprised repayments of the principal on loans. This split of loan repayments is not available from SIHs conducted prior to 2003-04.
  • A fuller measure of housing costs would include a range of outlays not collected in the SIH, but which are necessary to ensure that the dwelling can continue to provide an appropriate level of housing services. These include repairs, maintenance and dwelling insurance, and are costs that tend to be incurred by owner occupier households but not by renting households. Previous HES data shows that if these costs were added to SIH housing costs estimates, the estimates of average housing costs in this publication would be more than doubled for owners without a mortgage and would increase by about 15% for owners with a mortgage. (Appendix 1 outlines differences between the housing costs estimates available from the SIH and the HES. Paragraph 78 provides references for the HES).


Housing costs and household income

16 Housing costs can be a major component of total living costs. Therefore housing costs are often analysed as a proportion of total income, sometimes referred to as affordability ratios, and this publication presents a variety of housing cost/income ratio measures. However, comparisons between these measures are subject to the limitations of housing cost estimates obtained in the SIH that are described in the previous paragraph. Housing affordability ratios derived from SIH data are further impacted by the inclusion of CRA in the value of income collected. CRA is estimated, on average, to represent about 8% of the reported income of households receiving CRA and about 2% of the reported income of all households renting from landlords other than the state/territory authorities.


17 To illustrate the difficulties discussed above, consider two households that are renting their dwellings. Both receive government pensions of $400 per week. One rents from a public housing authority and pays rent of $100 per week. The other pays $135 rent per week to a private landlord and receives Commonwealth Rent Assistance of $35. In SIH, the housing costs of the latter household would be recorded as $135 and their income would be recorded as $435. The couple renting from the public housing authority has a housing costs/income ratio of 25%. The housing costs/income ratio for the latter household would be derived as 31%. If CRA receipts are excluded from housing costs and income the housing costs/income ratio for the latter couple is also 25%, highlighting that there is no substantive difference between the housing costs or income situation of the two couples. This anomaly is of particular concern when considering changes in affordability ratios over time, since there has been a shift from providing public housing to providing CRA as a means of supplying affordable housing to low income people.


18 While housing costs can be a major component of total living costs, the difference between the housing costs of a larger household and a smaller household would not be expected to be as great as the difference in many other costs, such as food or clothing. In other words, larger households can be expected to experience economies of scale in the supply of housing. This means that if a larger household and smaller household both have the same standard of living, it could be expected that on average the larger household will have a lower housing costs/income ratio. Therefore relatively high housing costs/income ratios are more of a concern with respect to larger households than smaller households. This should be borne in mind when comparing ratios across different household sizes.


19 In comparing households' housing costs with their income, it should be borne in mind that households have a variety of housing preferences. Some people may choose to live in an area with high land values because it is close to their place of employment and therefore they have lower transport costs. Some people choose to incur relatively high housing costs because they prefer a relatively high standard of housing instead of other consumption possibilities. High mortgage repayments might reflect a choice to purchase a relatively expensive home, or pay off a mortgage relatively rapidly, as a form of investment.


20 In this issue, households with nil or negative income have been excluded from calculations of housing costs as a proportion of gross income. These households make up 0.5% of all households.


21 Some households report extremely low income in the survey, which places them well below the safety net of income support by social security pensions and allowances. As explained in paragraphs 41 to 44 below, the incomes of these people are not always an appropriate indicator of the economic resources available to them. These households are likely to have a high ratio of housing costs as a proportion of gross income.



Housing stress

22 Households with relatively low income and housing costs greater than a certain proportion of income, often 30%, are sometimes said to be in "housing stress". This publication has not included such measures because of the lack of comparability of the housing affordability ratios across tenure and landlord types, the lack of general acceptance of such a threshold as an indicator of 'stress' when it often reflects investment and consumption preferences, and the difficulties of comparing across different household sizes, as described in the previous paragraphs. However, Table 5 does provide information separately for lower income households. Lower income households are defined here as those containing the 30% of people with equivalised disposable household income between the 10th and 40th percentiles.



Housing utilisation

23 The concept of housing utilisation in this publication is based upon a comparison of the number of bedrooms in a dwelling with a series of household demographics such as the number of usual residents, their relationship to one another, age and sex. There is no single standard or measure for housing utilisation. However the Canadian National Occupancy Standard presented in this publication is widely used internationally.


24 The Canadian National Occupancy Standard for housing appropriateness is sensitive to both household size and composition. The measure assesses the bedroom requirements of a household by specifying that:

  • there should be no more than two persons per bedroom
  • children less than 5 years of age of different sexes may reasonably share a bedroom
  • children less than 18 years of age and of the same sex may reasonably share a bedroom
  • single household members 18 and over should have a separate bedroom, as should parents or couples.

25 Households living in dwellings where this standard cannot be met are considered to be overcrowded.



Tenure type and landlord type

26 The concept of housing tenure is based on the type of legal right of the occupant to occupy the dwelling. Tenure is determined according to whether the household owns the dwelling outright, owns the dwelling but has a mortgage or loan secured against it, is paying rent to live in the dwelling or has some other arrangement to occupy the dwelling.


27 Owners are divided into two categories - owners with mortgages and owners without mortgages. A household's tenure type is owner with a mortgage if there is any outstanding mortgage or loan secured against the dwelling. This mortgage or loan may have been initially obtained primarily for either the purchase or the building of the dwelling, or for undertaking alterations or additions, or for some other purpose such as the purchase of a vehicle or an investment property. However, mortgage payments where the initial purpose of the loan was not primarily for housing are not treated as housing costs. A household's tenure type is owner without a mortgage if there are no loans or mortgages secured against the dwelling.


28 Renters are occupants who pay money as rent to another person or organisation, referred to as the landlord, in return for being allowed to occupy the dwelling. Renters can be further classified according to type of landlord. The landlord may be a relative or an unrelated person in another dwelling, or can be a real estate agency, a state or territory housing authority, a community organisation, a trust, or an employer.



Income

29 Income refers to regular and recurring cash receipts from employment, investments and transfers from government, private institutions and other households.


30 Sources from which income may be received include:

  • wages and salaries (whether from an employer or own corporate enterprise), including income provided as part of a salary sacrifice agreement
  • profit/loss from own unincorporated business (including partnerships)
  • investment income (interest, rent, dividends, royalties)
  • government (pensions and allowances)
  • private cash transfers (e.g. superannuation, regular workers' compensation, income from annuities, child support, and other transfers from other households).

31 Receipts which are excluded from income because they are not regular or recurring cash payments include:
  • income in kind including employee benefits such as the provision of a house or a car and employer contributions to pension and superannuation funds, except when provided as part of a salary sacrifice arrangement
  • capital transfers such as inheritances and legacies, maturity payments on life insurance policies, lump sum compensation for injuries or other damage
  • capital gains and losses.

32 Receipts of family tax benefit are treated as income, regardless of whether they are received fortnightly or as a lump sum. The aged persons' savings bonus and self-funded retirees' supplementary bonus, paid as part of the introduction of The New Tax System in 2000-01, are regarded as capital transfers as they were designed to help retired people maintain the value of their savings and investments following the introduction of the GST. However, the one-off payment to seniors paid in 2000-01, the one-off payment to families in 2003-04 and the one-off payment to carers paid in 2003-04, 2004-05 and 2005-06 are included as income as they were primarily a supplement to existing government support payments. The maternity payment introduced in July 2004 is also included as income.



Weekly income

33 Income is collected using a number of different reporting periods, such as the whole financial year for own unincorporated business and investment income, and the usual payment for a period close to time of interview for wages and salaries, other sources of private income and government pensions and allowances. The income reported is divided by the number of weeks in the reporting period. Estimates of weekly income in this publication therefore do not refer to a given week within the reference year of the survey.



Gross income

34 Gross income is the sum of the income from all sources before income tax and the Medicare levy have been deducted. Prior to 2005-06, family tax benefit paid through the tax system or as a lump sum was excluded from gross income for practical reasons. In 2005-06 these payments have been included in gross income.



Disposable income

35 Disposable income better represents the economic resources available to meet the needs of households. It is derived by deducting estimates of personal income tax and the Medicare levy from gross income.


36 Income tax and Medicare levy payments are estimated for all households using taxation criteria for 2005-06 and the income and other characteristics of household members reported in the survey.


37 Prior to 2005-06 the derivation of disposable income also included the addition of family tax benefit paid through the tax system or as a lump sum by Centrelink since for practical reasons it was not included in the gross income estimates.



Equivalised disposable income

38 Analyses by income quintile in this publication use equivalised disposable income rather than gross or disposable income since it enables comparison of the relative economic wellbeing of households of different size and composition. Equivalised disposable income is calculated by adjusting disposable income by the application of an equivalence scale. This adjustment reflects the requirement for a larger household to have a higher level of income to achieve the same standard of living as a smaller household. Where disposable income is negative, it is set to zero equivalised disposable income.


39 When household income is adjusted according to an equivalence scale, the equivalised income can be viewed as an indicator of the economic resources available to a standardised household. For a lone person household, it is equal to income received. For a household comprising more than one person, equivalised income is an indicator of the household income that would be required by a lone person household in order to enjoy the same level of economic wellbeing as the household in question.


40 For more information on the use of equivalence scales, readers are referred to Appendix 3 in Household Income and Income Distribution, Australia, 2005-06 (cat. no. 6523.0).



Lowest income decile

41 While equivalised income generally provides a useful indicator of economic wellbeing, there are some circumstances which present particular difficulties. Some households report extremely low and even negative income in the survey, which places them well below the safety net of income support provided by social security pensions and allowances. Households may under-report their incomes in the survey at all income levels, including low income households. However, households can correctly report low levels of income if they incur losses in their unincorporated business or have negative returns from their other investments.


42 Studies of income and expenditure reported in HES surveys have shown that such households in the bottom income decile and with negative gross incomes tend to have expenditure levels that are comparable to those of households with higher income levels (and slightly above the average expenditures recorded for the fifth income decile). This suggests that these households have access to economic resources such as wealth, or that the instance of low or negative income is temporary, perhaps reflecting business or investment start up. Other households in the lowest income decile in past surveys had average incomes at about the level of the single pension rate, were predominantly single person households, and their principal source of income was largely government pensions and allowances. However, on average, these households also had expenditures above the average of the households in the second income decile, which is not inconsistent with the use of assets to maintain a higher standard of living than implied by their incomes alone.


43 It can therefore be reasonably concluded that many of the households included in the lowest income decile are unlikely to be suffering extremely low levels of economic wellbeing. Income distribution analysis may lead to inappropriate conclusions if such households are used as the basis for assessing low levels of economic wellbeing. For this reason, tables showing statistics classified by income quintile include a supplementary category comprising the second and third income deciles, which can be used as an alternative to the lowest income quintile. (For an explanation of quintiles and deciles, see Appendix 1 of Household Income and Income Distribution, Australia, 2005-06 (cat. no. 6523.0)).


44 With the 2003-04 HES, analysis of households in the lowest income decile was improved through direct observation of the expenditure and net worth of these households. An examination of these low income households was presented in Appendix 4 of Household Household Wealth and Wealth Distribution, Australia, 2003-04 (cat. no. 6554.0).



Income quintiles

45 In this publication, the income quintiles are calculated with respect to persons, including children. Such measures are sometimes known as person weighted estimates. Nevertheless, as most of the relevant characteristics of persons relate to their household circumstances, most of the tables in this publication primarily describe households.



SURVEY METHODOLOGY

Scope and coverage

46 The survey collects information by personal interview from usual residents of private dwellings in urban and rural areas of Australia, covering about 98 per cent of the people living in Australia. Private dwellings are houses, flats, home units, caravans, garages, tents and other structures that are used as places of residence at the time of interview. Long-stay caravan parks are also included. These are distinct from non-private dwellings which include hotels, boarding schools, boarding houses and institutions. Residents of non-private dwellings are excluded.


47 The survey also excludes:

  • households which contain members of non-Australian defence forces stationed in Australia
  • households which contain diplomatic personnel of overseas governments
  • households in collection districts defined as very remote - this has only a minor impact on aggregate estimates except in the Northern Territory where such households account for about 24% of the population.


Data collection

48 Information for each household was collected using:
  • a household level computer assisted interview questionnaire which collected information on household characteristics, assets and liabilities
  • an individual level computer assisted interview questionnaire which collected information on income and other personal characteristics from each usual resident aged 15 years and over.

49 Sample copies of the above documents are included in the Information Paper: Survey of Income and Housing, User Guide, Australia, 2005-06 (cat. no. 6553.0).



Sample design

50 The sample was designed to produce reliable estimates for broad aggregates for households resident in private dwellings aggregated for Australia, for each state and for the capital cities in each state and territory. More detailed estimates should be used with caution, especially for Tasmania, the Northern Territory and the Australian Capital Territory.


51 For the 2005-06 SIH, dwellings were selected through a stratified, multi-stage cluster design. Selections were distributed across a twelve month enumeration period so that the survey results would be representative of income patterns across the year. In the final quarter of enumeration, 25% of the selected dwellings were deselected from the sample. This reduced the overall number of dwellings selected to participate in the survey. This outcome will increase the standard error in the final quarter estimates and hence the standard error in the annualised estimates. This increase in standard error is included in the error estimation. The relative change in sample size across the enumeration quarters may also introduce some bias to the annualised estimates but this is expected to be much less than the standard error.



Non-responding households

52 Of the selected dwellings there were 12,311 in the scope of the survey. Of these, 2,350 did not respond at all to the questionnaire, or did not respond adequately. Such households included:

  • households affected by death or illness of a household member
  • households in which the significant person(s) in the household did not respond because they could not be contacted, had language problems or refused to participate
  • households in which the significant person(s) did not respond to key questions.


Partial response and imputation

53 Some other households did not supply all the required information but supplied sufficient information to be retained in the sample. Such partial response occurs when:
  • income or other data in a questionnaire are missing from one or more non-significant person's records because they are unable or unwilling to provide the data
  • all key questions are answered by the significant person(s) but other data are missing.

54 In these cases, the data provided are retained and the missing data are imputed by replacing each missing value with a value reported by another person (referred to as the donor).


55 Donor records are selected by finding fully responding persons with matching information on various characteristics (such as state, sex, age, labour force status and income) as the person with missing information. As far as possible, the imputed information is an appropriate proxy for the information that is missing. Depending on which values are to be imputed, donors are randomly chosen from the pool of individual records with complete information for the block of questions where the missing information occurs.


56 In previous SIH surveys, responses were also imputed when not every person aged 15 or over residing in the household responded, but the significant person(s) provided answers to all key questions. In 2005-06 these households were regarded as non-responding.



Final sample

57 The final sample on which estimates were based is composed of persons for which all necessary information is available. The information may have been wholly provided at the interview (fully-responding) or may have been completed through imputation for partially responding households. Of the selected dwellings, there were 12,311 in the scope of the survey, of which 9,961 (80.9%) were included as part of the final estimates. The final sample consists of those 9,961 households, comprising 19,212 persons aged 15 years old and over. The final sample includes 2,441 households which had at least one imputed value in either income or assets and liabilities. For 57% of these households only a single value was missing, and most of these were for superannuation assets or a minor source of income for the household.

SIH FINAL SAMPLE: NUMBER OF HOUSEHOLDS, 2005-06

Capital city
Balance of State
Total
Households
Persons(a)
Households
Persons(a)
Households
Persons(a)
no.
no.
no.
no.
no.
no.

NSW
1 415
2 879
948
1 807
2 363
4 686
Vic.
1 247
2 478
596
1 102
1 843
3 580
Qld
798
1 530
896
1 753
1 694
3 283
SA
1 037
1 934
295
534
1 332
2 468
WA
1 031
1 987
335
622
1 366
2 609
Tas.
337
641
440
787
777
1 428
NT
117
246
46
82
163
328
ACT
423
830
-
-
423
830
Aust.
6 405
12 525
3 556
6 687
9 961
19 212

- nil or rounded to zero (including null cells)
(a) Number of persons aged 15 years and over



Weighting

58 Weighting is the process of adjusting results from a sample survey to infer results for the total in scope population whether that be persons or households. To do this, a 'weight' is allocated to each sample unit e.g. a person or a household. The weight is a value which indicates how many population units are represented by the sample unit. The first step in calculating weights for each unit is to assign an initial weight, which is the inverse of the probability of being selected in the survey. For example, if the probability of a household being selected in the survey was 1 in 600, then the household would have an initial weight of 600 (that is, it represents 600 households).


59 The initial weights are then calibrated to align with independent estimates of the population of interest, referred to as 'benchmarks'. Weights calibrated against population benchmarks ensure that the survey estimates conform to the independently estimated distribution of the population rather than to the distribution within the sample itself.


60 The SIH survey was benchmarked to the in scope estimated resident population (ERP) and the estimated number of households in the population.


61 Three types of benchmarks are used in the calibration of the final weights:

  • numbers of persons aged 15 and over
  • numbers of children under age 15
  • numbers of households.

62 Person benchmarks for persons aged 15 and over are estimates of the number of people in each state and territory by age and sex, the number of people in each state and the ACT by labour force status, and the number of people in each state living in the capital city or the balance of the state.


63 The benchmark variables used are the same as those used in the 2003-04 SIH. The only change has been in the age groups which now consist of mainly 5 year groups instead of 10 year groups, and extending the benchmarking for older ages by splitting a broad category for those aged 65 years and over into three categories for 65-69 years, 70-74 years and 75 years and over. The expanded detail for age groups in SIH 2005-06 aims to improve estimates across all ages, but particularly for older people. The impact of this change on all other estimates not involving age is expected to be minimal.


64 A separate set of benchmarks is used for children aged under 15, since there are not individual person records for them in the survey. Information about children is recorded on household records, however, and benchmarks for the number of children aged 0-4 and aged 5-14 are used for each state and territory.


65 Numbers of households are calibrated to benchmarks for total Australia with respect to household composition (based on the number of adults (1, 2 or 3+) and whether or not the household contains children).


66 The person and household benchmarks are based on estimates of numbers of persons and households in Australia. The benchmarks are adjusted to include persons and households residing in private dwellings only and therefore do not, and are not intended to, match estimates of the Australian resident population published in other ABS publications.



Estimation

67 Estimates produced from the survey are usually in the form of averages (e.g. mean weekly housing costs of couples with dependent children), or counts (e.g. total number of households that own their dwelling or total number of persons living in households that own their own dwelling). For counts of households, the estimate is obtained by summing the weights of all households in the required group (e.g. those owning their own dwelling). For counts of persons, the household weights are multiplied by the number of persons in the household before summing.


68 Estimates of means in this publication are obtained by multiplying the value for each household by the weight of the household, summing across all households and then dividing by the estimated number of households. For example, the mean housing costs of couple households with dependent children is the weighted sum of the housing costs of each such household divided by the estimated number of those households.



RELIABILITY OF ESTIMATES

69 The estimates provided in this publication are subject to two types of error, non-sampling and sampling error.



Non-sampling error

70 Non-sampling error can occur in any collection, whether the estimates are derived from a sample or from a complete collection such as a census. Sources of non-sampling error include non-response, errors in reporting by respondents or recording of answers by interviewers, and errors in coding and processing the data.


71 Non-sampling errors are difficult to quantify in any collection. However, every effort is made to reduce non-sampling error to a minimum by careful design and testing of the questionnaire, training of interviewers, and extensive editing and quality control procedures at all stages of data processing.


72 One of the main sources of non-sampling error is non-response by persons selected in the survey. Non-response occurs when people cannot or will not cooperate or cannot be contacted. Non-response can affect the reliability of results and can introduce a bias. The magnitude of any bias depends upon the level of non-response and the extent of the difference between the characteristics of those people who responded to the survey and those who did not.


73 The following methods were adopted to reduce the level and impact of non-response:

  • face-to-face interviews with respondents
  • the use of interviewers who could speak languages other than English, where necessary
  • follow-up of respondents if there was initially no response
  • imputation of missing values
  • ensuring that the weighted data is representative of the population (in terms of demographic characteristics) by aligning the estimates with population benchmarks.


Sampling error

74 The estimates are based on a sample of possible observations and are subject to sampling variability. The estimates may therefore differ from the figures that would have been produced if information had been collected for all households. A measure of the sampling error for a given estimate is provided by the standard error, which may be expressed as a percentage of the estimate (relative standard error). Further information on sampling error is given in Appendix 2.



ACKNOWLEDGEMENT

75 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated: without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.



SPECIAL DATA SERVICES

76 The ABS offers specialist consultancy services to assist clients with more complex statistical information needs. Clients may wish to have the unit record data analysed according to their own needs, or require tailored tables incorporating data items and populations as requested by them. Tables and other analytic outputs can be made available electronically or in printed form. However, as the level of detail or disaggregation increases with detailed requests, the number of contributors to data cells decreases. This may result in some requested information not being able to be released due to confidentiality or sampling variability constraints. All specialist consultancy services attract a service charge, and clients will be provided with a quote before information is supplied. For further information, contact ABS information consultants on 1300 135 070.



UNIT RECORD FILE

77 A basic confidentialised unit record file (CURF) from the 2005-06 SIH is available on CD-ROM. A more detailed SIH CURF is also available through the ABS Remote Access Data Laboratory (RADL). A full range of up-to-date information about the availability of ABS CURFs and about applying for access to CURFs is available via the ABS web site <http://www.abs.gov.au> (see Services We Provide, Confidentialised Unit Record Files (CURFs)). Inquiries to the ABS Microdata Access Strategies Section can be emailed to: microdata.access@abs.gov.au. Alternatively, telephone the section on (02) 6252 7714.



RELATED PUBLICATIONS

78 Users may wish to refer to the following ABS products:


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