INTEGRATION OF HES AND SIH
The 2003-04 SIH was integrated with the 2003-04 HES. This integration was achieved by selecting a subsample of the households in the SIH survey and asking them the additional questions required for HES purposes. The HES subsample comprised 6,957 of the 11,361 households responding to the SIH. The main advantages of integrating the surveys are:
- respondent burden is lower
- the data collection costs are lower
- the resultant dataset is richer because HES and SIH results are more comparable than previously.
However, in order to achieve this integration, some changes were required to both surveys which impact on comparability with previous surveys.
In addition, it is possible that the integration of the surveys affected the non-response bias in the SIH. The response rates for the HES subsample are lower than achieved in the SIH-only sample component because of the reluctance of some respondents to provide the extra information required in the HES part of the survey. The non respondents to the 2003-04 survey may therefore have different characteristics to the non respondents of previous SIHs, resulting in different non-response biases.
DATA ITEMS REMOVED
A few data items collected in previous surveys were not collected in the 2003-04 SIH. These include:
- income unit level tenure - in 2003-04 tenure is available at the household level only
- labour force status in each of the 7 months prior to the interview
- full-time/part-time status in each of the 7 months prior to the interview
- month left school.
CHANGES IN CONCEPTS, DEFINITIONS AND CLASSIFICATIONS
In previous SIHs, the household reference person was chosen from an income unit within the household that had the highest tenure type. Tenure type has been collected for households but not for income units in the 2003-04 SIH. The tenure type of income units is therefore no longer used in determining which person in the household is to be designated as household reference person.
In the published output from the surveys, the data item "family composition of household" replaces the item "household composition". The new item better meets user requirements for the treatment of households with dependent children.
CHANGES IN METHODOLOGY
There were a number of changes to the survey methodology introduced in 2003-04. Some of these were a consequence of the integration of the HES and SIH. The main changes which could impact on all data items were:
- previous SIH cycles had selected dwellings from those that had been respondents for eight months in the Monthly Population Survey (MPS), whereas in 2003-04 the SIH sample was drawn from dwellings not recently included in an ABS household survey (possible change in response bias)
- the sample size of the SIH was increased from 10,211 households (comprising 19,400 persons aged 15 and over) in 2002-03 to 11,361 households (comprising 22,315 persons aged 15 and over) in 2003-04 (lower sample error)
- interviewer use of a laptop computer (this may have improved data capture)
- editing and imputation procedures were changed - in particular because the SIH sample is no longer drawn from households who have participated in the MPS, responses given in the MPS are no longer available as a basis for imputation.
The changes in survey methodology relating to specific data items were:
- current income from own unincorporated business and investments was measured using respondents' estimates of expected income in the current financial year, whereas previously these data items were estimated based only on information about reported income for the previous financial year - this change had a significant impact on the coverage of such income streams in current income measures
- the collection of details about the assets and liabilities of the household may have improved the quality of reporting of associated income streams
- the instrument wording has been changed to explicitly ask that reported dividends include the value of imputation credits - previously this direction was only included in interviewer instructions
- information relating to some household loans was collected using a different methodology - for those loan accounts that have a redraw facility and have regular income (such as wages) deposited into them, respondents were not asked to provide a 'usual repayment' - instead they were asked to provide the amount that the principal outstanding usually decreases by in a 6 month period and this was used in conjunction with information collected on interest to derive a repayment amount
- details of previous financial year income were collected from all persons - in previous SIHs this information was not collected from people who had only arrived in Australia in the current financial year
- details of hours worked were collected from all employed persons - in previous SIHs, this information was only available for employees
- unlike previous SIHs, data on repayments and principal outstanding on mortgages for other purposes (ie for purposes other than building, buying, altering or adding to the selected dwelling) excludes mortgages that were used for business or investment purposes.