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EXPLANATORY NOTES


INTRODUCTION

1 This publication presents results which were compiled from data collected in the inaugural Multi-Purpose Household Survey (MPHS) that was conducted throughout Australia as a supplement to the Labour Force Survey (LFS) each month from August 2004 to June 2005. In future years, the survey will be conducted over the full financial year.

2 The MPHS was designed to provide statistics annually for a number of small, self-contained topics. These include both labour topics and other social and economic topics. The topics collected in 2004-05 were:

• Barriers and Incentives to Labour Force Participation
• Retirement and Retirement Intentions
• Household Use of Information Technology (HUIT)

HISTORICAL COMPARISONS

4 Due to the difference in the scope of previous surveys, previous person level data on household use of information technology which is comparable with the 2004-05 survey is only available up until 2002. The HUIT data for 2003 was obtained from the Survey of Disability, Ageing and Carers (SDAC), and person level data from this survey only relates to persons with a disability aged 15 years or over, and is thus not comparable with results from MPHS 2004-05. SDAC data are comparable at the household level.

5 In addition, the 2002 HUIT data were obtained from the GSS using a face-to-face randomly selected person methodology. MPHS questions were asked using a telephone interview. The ABS has taken reasonable steps during the survey development process to ensure that this change in collection methodology does not affect the quality of the data, but a small impact for the more complex questions cannot be ruled out.

DATA COLLECTION-MPHS

6 The Multi-Purpose Household Survey (MPHS) is conducted as a supplement to the monthly Labour Force Survey. One third of the dwellings in the outgoing rotation group (one eighth of the sample is rotated out each month) are selected for the MPHS. In these dwellings, after LFS has been fully completed for each person in scope and coverage, a person (usual resident) aged 18 and over is selected at random (based on a computer algorithm) and asked the additional MPHS questions in a personal interview. Data are collected using Computer Assisted Interviewing (CAI), whereby responses are recorded directly onto an electronic questionnaire in a notebook computer during a telephone interview.

7 The sample was accumulated over an eleven month period (August 2004 to June 2005). It was not enumerated in July 2004 due to a delay in full implementation of CAI for the LFS.

8 The publication Labour Force, Australia (Cat. no. 6202.0) contains information about survey design, sample redesign, scope, coverage and population benchmarks relevant to the monthly LFS, which also apply to supplementary surveys. It also contains definitions of demographic and labour force characteristics, and information about telephone interviewing relevant to both the monthly LFS and supplementary surveys.

SCOPE OF LFS AND MPHS

9 The scope of the LFS is restricted to people aged 15 years and over and excludes the following persons:

• members of the permanent defence forces
• certain diplomatic personnel of overseas governments, customarily excluded from census and estimated populations
• overseas residents in Australia
• members of non-Australian defence forces (and their dependants).

• people under the age of 18 years
• people living in private dwellings in very remote parts of Australia
• people living in special dwellings such as hotels, university residences etc
• Students at boarding schools, patients in hospitals, residents of homes (e.g. retirement homes, homes for persons with disabilities), and inmates of prisons
• visitors to private dwellings
• people living in very remote indigenous communities.

COVERAGE

12 In the LFS, coverage rules are applied which aim to ensure that each person is associated with only one dwelling and hence has only one chance of selection in the survey. See Labour Force, Australia (Cat. no. 6202.0) for more details.

SAMPLE SIZE FOR MPHS

13 The initial sample for the MPHS 2004-2005 consisted of 18,148 private dwelling households. Of the 15,524 private dwelling households that remained in the survey after sample loss and fully responding to the LFS (for example, households selected in the survey which had no residents in scope for the LFS, vacant or derelict dwellings and dwellings under construction), approximately 13,422 or 86% were fully responding to the MPHS.

WEIGHTING, BENCHMARKING AND ESTIMATION

14 Weighting is the process of adjusting results from a sample survey to infer results for the total in scope population. To do this, a 'weight' is allocated to each sample unit, which, for the MPHS, can be either 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. The initial weights are then calibrated to align with independent estimates of the population of interest, referred to as 'benchmarks'. Weights are calibrated against population benchmarks to ensure that the survey estimates conform to the independently estimated distribution of the population rather than the distribution within the sample itself.

Benchmarking

15 The survey was benchmarked to the estimated civilian population aged 18 years and over living in private dwellings in each state and territory in non-sparsely settled areas. The process of weighting ensures that the survey estimates conform to person benchmarks by state, part of state, age and sex and to household benchmarks by state, part of state and household composition. These benchmarks are produced from estimates of the resident population derived independently of the survey.

Estimation

16 Survey estimates of counts of persons or households are obtained by summing the weights of persons or households with the characteristic of interest.

IMPUTATION FOR NON RESPONSE

17 Certain data items such as estimates of income had significant non-response for 2004-2005. The ABS has not applied any imputation methodology for estimation of values for non-responses.

INCOME LESS THAN ZERO

18 Some households reported negative income in the survey. This is possible if they incur losses in their unincorporated businesses or have negative returns from their investments. Studies of income and expenditure from the 1998-99 Household Expenditure Survey (HES) 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 decile), indicating 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.

EQUIVALISED GROSS HOUSEHOLD INCOME QUINTILES

19 These are groupings of 20% of the total population when ranked in ascending order according to equivalised gross household income. The population used for this purpose includes all people living in private dwellings, including children and other persons under the age of 18 years. As the scope of this publication is restricted to only those persons aged 18 years and over, the distribution of this smaller population across the quintiles is not necessarily the same as it is for persons of all ages, i.e. the percentage of persons aged 18 years and over in each of these quintiles may be larger or smaller than 20%.

20 Equivalence scales are used to adjust the actual incomes of households in a way that enables the analysis of the relative wellbeing of people living in households of different size and composition. For example, it would be expected that a household comprising two people would normally need more income than a lone person household if all the people in the two households are to enjoy the same material standards of living. Adopting a per capita analysis would address one aspect of household size difference, but would address neither compositional difference (i.e. the number of adults compared with the number of children) nor the economies derived from living together.

21 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.

22 The equivalence scale used in this publication was developed for the Organisation for Economic Co-operation and Development and is referred to as the "modified OECD" equivalence scale. It is widely accepted among Australian analysts of income distribution.

23 The scale allocates 1.0 point for the first adult (aged 15 years or older) in a household; 0.5 for each additional adult; and 0.3 for each child. Equivalised household income is derived by dividing total household income by the sum of the equivalence points allocated to household members. For example, if a household received combined gross income of $2,100 per week and comprised two adults and two children (combined household equivalence points of 2.1), the equivalised gross household income for each household member would be calculated as $1,000 per week.

24 For more information on the use of equivalence scales, see Household Income and Income Distribution, Australia, 2003-04 (cat. no. 6523.0)

RELIABILITY OF ESTIMATES

25 The estimates provided in this publication are subject to sampling and non-sampling error.

Sampling error

26 Sampling error is the difference between the published estimates, derived from a sample of persons, and the value that would have been produced if all persons in scope of the survey had been included. For more information refer to the technical note.

Non-sampling error

27 Non-sampling error may occur in any collection, whether it is based on a sample or a full count such as a census. Sources of non-sample error include non-response, errors in reporting by respondents or recording of answers by interviewers, and errors in coding and processing data.

COMPARABILITY WITH MONTHLY LFS STATISTICS

28 Due to differences in the scope and sample size of the MPHS and that of the LFS, the estimation procedure may lead to some small variations between labour force estimates from this survey and those from the LFS.

FUTURE SURVEYS

29 The ABS will conduct the MPHS again during the 2005-06 financial year. The topics included in the 2005-06 MPHS are:

• Work related injuries
• Household use of information technology
• Participation in sport and physical activity
• Attendance at selected culture and leisure venues and events

RELATED PUBLICATIONS

31 Other ABS publications on the production and use of information and communication technologies and telecommunication goods and services in Australia are:

• Business Use of Information Technology, 2003-04 (Cat. no. 8129.0)
• Government Use of Information Technology, Australia, 2002-03 (Cat. no. 8119.0)
• Household Use of Information Technology, Australia, 2002 and 2003 (Cat. no. 8146.0)
• Information and Communication Technology, Australia, 2002-03 (Cat. no. 8126.0)
• Use of Information Technology on Farms, Australia, 2003-04 (Cat. no. 8150.0)
• Internet Activity, Australia, March 2005 (Cat. no. 8153.0)

ABS DATA AVAILABLE ON REQUEST

33 As well as statistics included in this and related publications, the ABS may have other relevant data available on request. Inquiries should be made to Siddhartha De, Canberra, (02) 6252 6519 or the National Information Referral Service on 1300 135 070.