Indicators from the 1996, 2001 and 2006 New Zealand Disability Surveys for monitoring progress on outcomes for disabled people
Purpose of this Report
The Office for Disability Issues has responsibility for monitoring outcomes for disabled people living in New Zealand. This includes assessing whether important aspects of the lives of disabled people are changing over time. To support this work, the Office contracted HealthSearch Ltd to provide a selection of New Zealand statistical data with potential to be used as a basis for monitoring outcomes for disabled people. In particular, a priority for the project was to identify potentially useful data comparing key outcomes for disabled people and non-disabled people over time. The information would be used, as appropriate and to the extent possible, for reporting on progress with implementing the New Zealand Disability Strategy and the United Nations Convention on the Rights of Persons with Disabilities.
New Zealand Disability Surveys
Following a brief review of the range of disability-related survey information available, we concluded that only the Disability Surveys conducted by Statistics New Zealand in 1996, 2001 and 2006 were likely to provide sufficiently relevant and robust information to satisfy the goals of the project in the time available. We therefore concentrated on identifying potentially suitable outcomes-related data from these three surveys. This is the data presented here.
Content of the report
The report is in two parts.
Part One presents a disability profile to set the context for the data shown in the remainder of the report. The profile indicates the numbers and proportions of people estimated to be disabled and not disabled in 1996, 2001 and 2006. This includes an analysis by age and ethnic group. Data on the types of disabilities people have, and the levels of support they need, are also summarised.
Part Two presents data on potentially useful social and economic indicators. For disabled and non-disabled people of all ages, data is presented on household composition, household income and the New Zealand Deprivation Index (NZDep). The latter is a measure of levels of socioeconomic deprivation in small geographic areas. Data is then presented on the educational qualifications, labour force status, occupation, personal income and partnership status of disabled and non-disabled adults. The last section looks at disabled children's attendance at mainstream classes and/or special units.
Data sources and analysis
The Disability Survey data included in this report was already available to the authors of this report; that is, no new data was ordered from Statistics New Zealand. The information was either in the form of published reports by other authors (for example, Statistics New Zealand 1998, 2002, 2007 and Health Funding Authority/Ministry of Health 1998) or in the form of published or raw data already held by HealthSearch Ltd as a result of work done for previous projects (for example, Ministry of Health/Intersectoral Advisory Group 2004, 2005 and Office for Disability Issues and Statistics New Zealand 2008, 2009, 2009a, 2010).
The particular social and economic topics covered in this report were selected because:
- they relate to issues included in the Office for Disability's Outcomes Framework (Office for Disability Issues 2009)
- data was able to be accessed within the project timeframe
- comparable data was available for non-disabled as well as disabled people
- data was available for at least two of the three Disability Surveys (one of the surveys being 2006)
- data was already available in, or could be reprocessed into, consistent categories across all three surveys.
Presenting the data
In each section of the report, charts are used to highlight selected survey data for 1996, 2001 and 2006 for disabled people and, where appropriate, disabled people compared with non-disabled people. Definitions are also given of relevant terms or categories used. If special caution is needed when considering the data in a section, this is noted in the text. Each section ends with a detailed table (or tables) showing all data compiled for the section.
All survey data has been ‘rated up' to provide estimates for the total number of disabled adults and children in New Zealand.
Estimates that are smaller than 50 percent relative sampling error (RSE) cut-off points have been excluded. A 50 percent RSE means, statistically, there is a 95 percent chance that a true value lies between plus or minus 50 percent of the calculated population estimate.1
All data shown in tables has been rounded to the nearest 100. This may result in a total in a table disagreeing slightly with the total of the individual items in the table. Where possible, percentages shown in the tables and charts have been calculated using unrounded data. Percentages also have been calculated using totals that include ‘not specified' or ‘not elsewhere included' categories.
People living in households
Unless otherwise stated, data in all sections of the report refer to disabled and non-disabled people (adults aged 15+ and/or children aged 0-14) living in households (i.e. private dwellings). One section of Part One of the report also includes data on how many adults live in residential facilities such as rest homes, continuing care hospitals and intellectual disability units. However, linked census data on social and economic outcomes are not available for these people, so they could not be included in Part Two of the report.
General cautions when considering the data in this report
Readers should take special note of the following technical issues relating to the 1996, 2001 and 2006 Disability Surveys and how data from them is reported here. Some of these issues may limit the extent to which the data presented here can be used as indicators for monitoring outcomes for disabled people, especially if the goal is to monitor changes over time.
1) Possible undercounting in 2006 Disability Survey. Rates of disability (the proportion of New Zealanders who are disabled) in the 2006 Disability Survey were lower than in the 1996 and 2001 surveys. For example, the 2006 survey identified 16 percent of people living in private households had a disability compared to 19 and 20 percent respectively in the 1996 and 2001 surveys (for more detail see the section Disability Rates in this report). Statistics New Zealand examined whether methodological and survey administration factors may have contributed to this result, rather than any ‘real' drop in the proportion of people reporting they have a disability. It concluded that the apparent decrease in disability rates ‘is likely to be due to a combination of minor and statistical and nonstatistical factors' (Statistics New Zealand 2007:22). Statistics New Zealand therefore indicates that ‘strong caution' should be used when comparing 2006 data with data from the 2001 and 1996 surveys. For further detail on this issue see Appendix A. This reproduces the section from the report New Zealand Disability Survey 2006: Hot off the Press (Statistics New Zealand 2007) discussing possible reasons for the apparent decrease. Dylan (2009) also comments on possible reasons for the apparent drop in disability rates in 2006.
2) Technical difficulties related to determining if differences between population estimates (and population rates calculated using these estimates) are statistically significant. In this report, we have not been able to determine if any of the differences identified between disabled and non-disabled people in each of the three survey years are statistically significant. For example, if the 2006 survey indicates that 8 percent of disabled people and 4 percent of non-disabled people have household incomes less than $15,001, it is not clear if this difference between disabled and non-disabled people is simply due to chance or is sufficiently robust statistically to be considered a true difference.
Similarly, we have not been able to determine if any of the differences identified across the three survey years are statistically significant (assuming it is legitimate to make such between-year comparisons, which it may not be, given the above discussed issue of the possible 2006 undercount).
Developing a methodology to identify if differences identified in the surveys are statistically significant is made difficult by the complex sampling procedures used in the surveys. There seems to be some scope to use relative sampling errors (RSEs) as a basis for assessing statistical significance, although currently the publicly-available RSE tables for the surveys, as calculated by Statistics New Zealand, do not appear to be sufficiently detailed for this purpose2
3) The survey data is mainly descriptive rather than explanatory. The tables in this report provide a snapshot of data for disabled and non-disabled people for the years 1996, 2001 and 2006. The data is essentially descriptive in that it records how many people are estimated to be employed, partnered, have post-school qualifications, and so on. For example, the 2006 survey indicates that 59 percent of disabled and 76 percent of non-disabled adults aged 15-64 are employed. However, in general, we have not provided commentary suggesting what factors may be important in producing this apparent difference between the employment rates of disabled and non-disabled 15-64 year olds. Identifying such factors would be a substantial research exercise and require further investigation not only of data from the Disability Surveys but also other New Zealand and overseas studies that have sought to unravel the possible origins of these differences using empirical analysis and theory.
1 See Appendix B for a list of the RSE cut-off points used in this report.
2 It was not possible to get more detailed RSEs from Statistics New Zealand for the purposes of the current project, although this may be possible in the future.