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4130.0 - Housing Occupancy and Costs, 2007-08  
Previous ISSUE Released at 11:30 AM (CANBERRA TIME) 06/11/2009   
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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 2007-08 and earlier Surveys of Income and Housing. 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 Survey of Income and Housing, Australia: User Guide, 2007-08 (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, 2005-06 and 2007-08. The 2007-08 SIH collected information from a sample of 9345 households over the period August 2007 to June 2008. Future cycles of the SIH will be conducted every two years.

4 The 2007-08 SIH included additional housing topics to enable reporting on the broader housing circumstances of non-Indigenous Australians. The ABS will collect additional housing information in the SIH every six years. In 2007-08, the additional topics include housing mobility, housing condition and dwelling characteristics, home purchase for first home buyers, loan financing for owners with a mortgage and rental arrangements. Summary data will be published in Housing Mobility and Conditions, Australia, 2007-08 (cat. no. 4130.0.55.002) in November 2009. Appendix 2 provides further information on these topics.

5 Other household collections conducted by the ABS which cover housing are:

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

6 Household 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 and 2008.

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


Changes in this issue

8 The 2007-08 SIH content was largely similar to that used in the 2005-06 SIH with some changes in questions, definitions and methodology.

9 Changes in this issue are:
  • the inclusion of a table on income unit tenure, following the collection of person and income unit tenure data for the first time since the 2002-03 SIH.
  • the inclusion of bonuses, irregular overtime, termination payments, inter-household transfers and non-cash benefits in income estimates for 2003-04, 2005-06 and 2007-08. For more information on improvements to the collection of income statistics see Appendix 4 of Household Income and Income Distribution, Australia, 2007-08 (cat. no. 6523.0).
  • the use of population and household benchmarks based on the 2006 Census. In 2005-06 these benchmarks were based on the 2001 Census. For further information see paragraphs 58 to 66.
  • the use of additional information about tenure within the household to influence the selection of the household reference person, consistent with the treatment used prior to the 2003-04 SIH.


CONCEPTS AND DEFINITIONS

10 The concepts and definitions relating to the statistics in this publication 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.


Income unit

13 Although the household has been adopted as the basic level of analysis in this publication, tenure data have been included on an income unit basis in table 36. An income unit is a single person or a group of related persons within a household, whose command over income is assumed to be shared. Income sharing is assumed to take place within married (registered or defacto) couples, and between parents and their dependent children.


Housing costs

14 Housing costs are the recurrent outlays by household members in providing for their shelter. The data collected in the SIH are limited to major cash outlays on housing, that is, mortgage repayments, rent, property and water rates as well as body corporate fees. Housing costs are shown in this publication as weekly equivalents.

15 Only payments which relate to the dwelling occupied by the household at 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.

16 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. 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 25% 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 2007-08 SIH indicated that about 32% of the housing costs of owners with a mortgage comprised repayments of the principal on loans. The equivalent proportions in 2005-06 and 2003-04 were 36% and 40% respectively.
  • 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 would be more than doubled for owners without a mortgage and would increase by about 15% for owners with a mortgage.


Housing costs and household income

17 Housing costs are often 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. 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 7% 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.

18 To illustrate the difficulties discussed above, consider two couples 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 per week. 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%. However, 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.

19 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.

20 In comparing households' housing costs with their income, it should be noted that households have a variety of housing preferences. Some people may choose to live in an area with high property 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 compared with 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.

21 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.

22 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 42 to 45 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 high housing costs/income ratios.


Housing stress

23 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

24 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.

25 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.

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


Tenure type and landlord type

27 The concept of housing tenure is based on the type of legal right of the occupant/s to occupy the dwelling. Tenure is determined according to whether the unit (household, income unit or person) 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.

28 In this publication, tenure information is provided at both the household and income unit levels. Person level tenure was also enumerated in the 2007-08 SIH and is available on the CURF. Tenure information at household, income unit and person levels enables users to analyse within household tenure arrangements, such as subletting and boarding. This detailed tenure data will also be available from future SIHs.

29 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.

30 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

31 Household income consists of all current receipts, whether monetary or in kind, that are received by the household or by individual members of the household, and which are available for, or intended to support, current consumption.

32 Income includes receipts from:
  • wages and salaries and other receipts from employment (whether from an employer or own incorporated enterprise), including income provided as part of salary sacrifice and/or salary package arrangements
  • profit/loss from own unincorporated business (including partnerships)
  • net investment income (interest, rent, dividends, royalties)
  • government pensions and allowances
  • private transfers (e.g. superannuation, workers' compensation, income from annuities, child support, and financial support received from family members not living in the same household).

33 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 older Australians paid in 2000-01, 2005-06, and 2007-08, the one-off payment to families paid since 2003-04 and the one-off payments to carers paid since 2003-04 are included as income as they were primarily a supplement to existing income support payments. The maternity payment introduced in July 2004 is also included as income.


Weekly income

34 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

35 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 and 2007-08 these payments have been included in gross income.


Disposable income

36 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. The Medicare levy surcharge was calculated for the first time in 2007-08 and was also deducted from gross income when calculating disposable income.

37 Income tax and Medicare levy payments are estimated for all households using taxation criteria for 2007-08 and the income and other characteristics of household members reported in the survey.

38 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

39 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.

40 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.

41 For more information on the use of equivalence scales, readers are referred to Appendix 3 in Household Income and Income Distribution, Australia, 2007-08 (cat. no. 6523.0).


Lowest income decile

42 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.

43 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.

44 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, 2007-08 (cat. no. 6523.0)).

45 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 Wealth and Wealth Distribution, Australia, 2003-04 (cat. no. 6554.0).


Income quintiles

46 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

47 The survey collects information by personal interview from usual residents of private dwellings in urban and rural areas of Australia (excluding very remote areas), covering about 97% of the people living in Australia. Private dwellings are houses, flats, home units, caravans, garages, tents and other structures that were 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.

48 Usual residents excludes:
  • households which contain members of non-Australian defence forces stationed in Australia, and
  • households which contain diplomatic personnel of overseas governments.


Data collection

49 Information for each household was collected using:
  • a household level computer assisted interview questionnaire which collected information on household characteristics
  • 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. It also collected information on child care costs, child care usage and barriers to labour force participation due to child care related reasons.

50 Sample copies of the above documents are included in the Survey of Income and Housing, User Guide, Australia, 2007-08 (cat. no. 6553.0).


Sample design

51 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 (see Appendix 3).

52 For the 2007-08 SIH, dwellings were selected through a stratified, multistage cluster design. Selections were distributed across an eleven month enumeration period. The SIH is normally conducted over a 12 month enumeration period so that the survey results would be representative of income patterns across the year. In 2007-08 the estimates were adjusted during weighting so that the shorter enumeration period in the first quarter was compensated in the final estimates. In the final quarter of enumeration, 10% of the selected dwellings were deselected from the sample. This reduced the overall number of dwellings selected to participate in the survey. This outcome may increase the standard error in the final quarter estimates and hence the standard error in the annualised estimates. 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

53 Of the selected dwellings there were 11,126 in scope of the survey. Of these, 1,781 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 had language problems or refused to participate
  • households in which the significant person(s) did not respond to key questions.


Partial response and imputation

54 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.

55 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).

56 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.


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 11,126 in the scope of the survey, of which 9,345 (84.0%) were included as part of the final estimates. The final sample consists of those 9,345 households, comprising 18,326 persons aged 15 years old and over. The final sample includes 2,026 households which had at least one imputed value in income or child care expenses. For 52% of these households only a single value was missing, and most of these were for income from interest and investments or information relating to household loans.

SIH FINAL SAMPLE:Number of households, 2007-08

CAPITAL CITY
BALANCE OF STATE
TOTAL
Households
Persons(a)
Households
Persons(a)
Households
Persons(a)
no.
no.
no.
no.
no.
no.

NSW
1 193
2 423
765
1 433
1 958
3 856
Vic
1 309
2 633
482
936
1 791
3 569
Qld
749
1 559
828
1 588
1 577
3 147
SA
1 063
2 016
292
544
1 355
2 560
WA
965
1 896
269
513
1 234
2 409
Tas
283
538
387
712
670
1 250
NT
268
538
64
128
332
666
ACT
428
869
-
-
428
869
Aust
6 258
12 472
3 087
5 854
9 345
18 326

- 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 An adjustment is then made to the initial weights to account for changes in the sample across the four quarters of survey enumeration; the sum of the weights after this initial adjustment of households in each quarter is equal.

60 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.

61 In the 2007-08 SIH, all persons in each household were assigned a weight. This differs from the 2005-06 SIH where children aged 0-14 years were not given separate weights, but household counts of the number of children were benchmarked to population totals.

62 The SIH survey was benchmarked to the in scope estimated resident population (ERP) and the estimated number of households in the population. The 2007-08 cycle has used population and household benchmarks based on the 2006 Population Census instead of the 2001 Population Census used for the 2003-04 and 2005-06 SIH. The differences in the estimated population that occur due to this change are outlined in the following table.

2001 Census
2006 Census

Population benchmark
Australian Population Benchmark(a)
21 074 415
21 178 235
Persons in Non Private Dwellings Excluded
392 257
371 636
Persons in Very Remote Excluded
173 102
163 470
Total Population Exclusions
565 359
535 106
Final Population Benchmark
20 509 056
20 643 129
Household benchmark
Australian Household Benchmark(a)
8 247 769
8 136 593
Households in Very Remote Excluded
61 690
61 348
Final Household Benchmark
8 186 079
8 075 244

(a) at 31 December 2007


63 The benchmarks used in the calibration of the final weights for the 2007-08 SIH were:
  • number of persons -
      • by state or territory by age by sex
      • five year age groups up to 80+ years for the states
      • five year age groups up to 75+ years for the ACT
      • five year age groups up to 60+ years for the NT
      • by state or the ACT by labour force status ('Employed', 'Unemployed' and 'Not in the labour force')
      • by state by capital city/balance of state.
  • numbers of households -
      • by household composition (number of adults (1, 2 or 3+) and whether or not the household contains children).

64 More detailed age groupings have been used where possible in the 2007-08 SIH. In the 2003-04 SIH, ten year age groups up to 65 years and over were used. In the 2005-06 SIH five year age groups were used up to 75 years and over, except for NT where the age groups were 15-24, 25-44, 45 and over. The 2007-08 age groups have been refined further where possible. Five year age groups up to 80 years or older were used in all states. For the two territories five year age groups up to 75 years or older for the ACT and 60 years or older for the NT were used. The expanded detail for age groups in the 2007-08 SIH aims to improve estimates across those ages. The impact of this change on estimates not involving age is expected to be minimal.

65 The person and household benchmarks were based on preliminary estimates of numbers of persons and households in Australia in 2007-08 based on the 2006 Population Census. The benchmarks used include households and persons residing in occupied private dwellings only and therefore do not, and are not intended to, match estimates of the total Australian resident population published by the ABS.

66 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).


Estimation

67 Estimates produced from the survey are usually in the form of averages (e.g. average weekly income of couple households 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 was obtained by summing the weights for the responding households in the required group (e.g. those owning their own dwelling). For counts of persons, the household weights were multiplied by the number of persons in the household before summing. The SIH collects data on the number of people, including children, in each household but separate records with income and other detailed data were only collected for people 15 years and older. Therefore, counts of persons cannot be obtained by summing the weights of all persons.

68 Average income values are obtained in two different ways, depending on whether mean gross household income or mean equivalised disposable household income is being derived. Estimates of mean gross household income are calculated on a household weighted basis. They are obtained by multiplying the gross income of 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 gross household income of couple households with dependent children is the weighted sum of the gross income of each such household divided by the estimated number of those households.

69 Estimates of mean equivalised disposable household income are calculated on a person weighted basis. They are obtained by multiplying the equivalised disposable income of each household by the number of people in the household (including children) and by the weight of the household, summing across all households and then dividing by the estimated number of people in the population group. Appendix 2 in Survey of Income and Housing, Australia: User Guide, 2007-08 (cat. no. 6553.0) illustrates the differences between mean gross household income calculated on a household weighted basis and mean equivalised disposable household income calculated on a person weighted basis.


RELIABILITY OF ESTIMATES

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


Non-sampling error

71 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.

72 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 data entry staff, and extensive editing and quality control procedures at all stages of data processing.

73 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.

74 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

75 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 3.


ACKNOWLEDGMENT

76 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

77 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 analytical 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 from 9:00am to 4:30pm AEST Monday to Friday (International callers +61 2 9268 4909).


UNIT RECORD FILE

78 A basic confidentialised unit record file (CURF) from the 2007-08 SIH is available on CD-ROM. A more detailed SIH CURF is also available through the ABS Remote Access Data Laboratory. All clients wishing to access the SIH 2007-08 basic and expanded CURF should refer to the ABS Website <http://www.abs.gov.au> (see Services, CURF Microdata) and read the CURF Microdata Entry Page, and other linked information, before downloading the appropriate Guide, Application and Undertaking forms and applying for access.


Australian universities

79 University clients should refer to the ABS web site <www.abs.gov.au> (see Services, Services for Universities). The SIH 2007-08 basic and expanded CURF can be accessed by universities participating in the ABS/Universities Australia CURF Agreement for research and teaching purposes.


Other clients

80 Other prospective clients should contact the Microdata Access Strategies Section of the ABS at <microdata.access@abs.gov.au> or on (02) 6252 7714.


RELATED PUBLICATIONS

81 Users may wish to refer to the following ABS products which are produced from the SIH:
82 Other ABS products which relate to housing statistics include:

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