Evaluation of the Australian Wage Subsidy Special Youth ...

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5.8 Model of the probability of attrition
To construct the weight for non-response and selection that was provided with the data,
administrative data was used to weight back to the population. Only survey data is
available to be applied to estimates of the sample attrition weight. As the attrition only
occurs after the 1984 survey, it is likely the survey information is the most relevant for
describing the characteristics of the respondents, as it is gathered at a more recent
juncture while the administrative data would be more dated. One useful piece of relevant
information that is not available in the data would be survey collection information about
movers. This variable had a central role in describing non-response. However,
unavailability means the importance of this item to attrition cannot be assessed. The
variables selected for explaining attrition are chosen from amongst those variables
measured in the 1984 survey. The model is weighted by the initial nonresponse/design/selection
weight in order to represent the 1984 data, so that the estimates
which will be used for the attrition weights will only account for the further non-response
to the later surveys to 1986. In this following model, it is assumed that the same process
as that of attrition to 1986 defines attrition to the 1985 survey. 138
The results of estimation for the probit model of attrition are shown in column 1 of table
5.9. Those who were interviewed in South Australia and the Northern Territory, Western
Australia and Tasmania, were more likely to also be interviewed in later years to 1986.
Additionally, those in country towns and rural areas, and those with a highest
qualification to year 12, had a higher tendency to be interviewed again in later years.
Those with longer unemployment prior to June 1984 were less likely to be surveyed
again in later years, as were those who were missing the unemployment variable, had
held longer jobs in the past, and those who were married. Participants in SYETP were
more likely to respond to later surveys.
138 In exploration of this, results for which are not shown, separate modelling of the attrition to each year
was not found to have different estimated models, with the same coefficients statistically significant and of
similar magnitude, and so common modelling of the attrition was found appropriate.