2 The data
The HWR survey was established by the School of Psychology at Massey University in collaboration with the Health Research Council of New Zealand, the New Zealand Institute for Research on Ageing and the Centre for Māori Health, Research and Development at Massey University, to investigate the factors surrounding work and retirement for those aged 55 to 70.[2] The first wave was run in 2006, with a total 6,662 respondents to a postal questionnaire.[3] The sample was drawn from the Electoral Roll[4], and those identifying as being of Māori descent were deliberately over sampled.
…equal probability sampling procedures were used to select both the general and Māori sub-samples for the HWR study. Both sub-samples were treated independently and random selection was used to select 55 to 70 year-old New Zealanders participants from each population of interest (the general and Māori respectively) to their respective sub-sample. (Towers, 2007)
A summary of the sample size is given in Table 2-1.Table 2-2 summarises the sample by age groups, and shows the number of usable observations. A total of 822 records were dropped as they did not report at least one of age, gender, ethnicity, physical or mental health status. The sample was further pruned of eleven cases by eliminating those whose reported age fell below 50. The sample was reweighted to reflect these adjustments. The weighting was done by ethnicity, as the population totals were provided for those values (Towers 2007). All results in Section 3 onwards are the weighted results unless otherwise indicated. Additionally, the wider age ranges are used, including those under 55 and over 70, unless otherwise indicated.
| Category | General Electoral Roll | of which those identifying as being of Māori descent |
|---|---|---|
| Total number of 55–70 year-olds | 609,000 | 47,436 |
| Sample drawn | 5,264 | 7,781 |
| Number excluded1 | 210 | 341 |
| Final sample | 5,054 | 7,440 |
| Response rate | 62% | 48% |
| Number of respondents | 3,133 | 3,529 |
| Total sample numbers available for analysis | 6,662 (corresponding to an overall response rate of 53%) | |
Note:
1 Excluded from the study as they were never able to participate (eg they were unable to be contacted, were deceased or had been institutionalised).
Note that not all observations can be used, as they may be dropped from models if they are missing values for variables other than the ones listed above.
| Age range | Total number of respondents | Number of usable observations | Number falling exactly in the age range |
|---|---|---|---|
| 55-591 | 2,838 | 2,306 | 1,995 |
| 60-64 | 1921 | 1,567 | 1,567 |
| 65-702 | 1,742 | 1,466 | 1,461 |
| Total | 6,6623 | 5,339 | 5,023 |
Notes:
1 Includes those observations aged less than 55 in the first two columns.
2 Includes those observations aged more than 70 in the first two columns.
3 Includes 161 observations with no determinable age, sex or ethnicity.
A complete listing of all the variables used in this study together with their definitions, means, medians and inter-quartile ranges, is set out in Appendix B.
Notes
- [2]For full details of the survey, methodology and results, see: http://hwr.massey.ac.nz/
- [3]The questionnaire used in the 2006 survey, the results of which are the basis for the present study, is available online at http://hwr.massey.ac.nz/surveys.htm
- [4]The Electoral Roll contains date of birth and provides for persons of Māori descent to identify as such.
