Department of Public Health, University of Otago, Wellington NZDep2018 Index of Deprivation June Atkinson1, Clare Salmond2, Peter Crampton3 Interim Research Report, December 2019 1 Senior Data Analyst, Department of Public Health, University of Otago, Wellington 2 Biostatistician, Private contractor, Wellington 3 Professor of Public Health, Kōhatu, Centre for Hauora Māori, University of Otago, Dunedin E-mail: [email protected] [email protected] [email protected] Address: PO Box 7343, Wellington, New Zealand Phone: 04 385 5541 (ext. 6085) Suggested citation: Atkinson J, Salmond C, Crampton P (2019). NZDep2018 Index of Deprivation, Interim Research Report, December 2019. Wellington: University of Otago. 1 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington Contents List of tables 5 List of figures 5 The authors 6 Acknowledgements 7 Ethics and confidentiality 7 Executive Summary 8 Why is this an interim report? 10 Introduction 11 NZDep methodological papers 12 NZDep research reports 13 Research papers illustrating applications of NZDep 13 Atlases 14 Aim 16 Purpose of indexes 16 Cautions 17 The indicator becomes the reality 17 Area versus individual measures 17 Relative versus absolute deprivation 18 Apparent simplicity 18 Longitudinal comparisons 18 Constructing the index 19 Overview 19 Data sources 19 Defining small areas 20 Choice of variables for inclusion in NZDep2018 21 The effect of mitigation 21 Variables in NZDep2018 22 Possible new candidate variables available in the 2018 census 22 2 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington Unchanged variables 23 Slightly modified variables 23 Internet access 24 Household income 24 Means tested benefit status 25 Creating the index 26 Validation 27 Results 28 Defining small areas 28 NZDep2018 scores 30 Comparison of NZDep2018 scores with those for NZDep2006 and NZDep2013 32 The NZDep2018 Index of deprivation 33 Variation within communities 34 Standardisation 36 Validation 37 Mapping 39 Appendix one: Source populations 44 Individual form data 44 Dwelling form data 44 Why do we use two different source populations? 45 Appendix two: Description of unchanged NZDep variables 46 Unemployed 46 Single parent families 46 No qualifications 46 Dwellings not owner occupied 47 Occupancy 47 Appendix three: Standardisation 49 Age and sex 49 Indirect standardisation 49 Ethnicity 50 3 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington Structural zeros 51 Not specified 51 Appendix five: Longitudinal analyses 52 Introduction 52 Comparing areas over time 53 Comparing relationships with deprivation over time 59 References 61 4 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington List of tables Table 1: Variables included in NZDep2018 22 Table 2: Number of Statistical Area 1s per NZDep2018 small area 28 Table 3: Distribution of the population in NZDep2018 small areas 29 Table 4: Weights for the first principal components of the NZDep2018 variables for three levels of mitigation 30 Table 5: Principal component summaries for three levels of mitigation using the variables included in the eventual NZDep2018 31 Table 6: Weights on the first principal components for 2006, 2013 and 2018 32 Table 7: Crowding index 48 Table 8: Comparison of the NZDep score distributions from 1996 to 2018 56 List of figures Figure 1: Distribution of NZDep2018 scores, with the NZDep2018 decile scale superimposed 34 Figure 2: Variation in NZDep2018 profiles 35 Figure 3: Regular smoking by deciles of NZDep2018 and NZDep2013 38 Figure 4: NZDep2018 distribution in the North Island of New Zealand 40 Figure 5: NZDep2018 distribution in the South Island of New Zealand 41 Figure 6: Comparing deprivation deciles over time using hypothetical outcome data 60 5 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington The authors June Atkinson (NZC Statistics) is a Senior Data Analyst in the Department of Public Health, University of Otago, Wellington. She is an expert user of the statistical software suite (produced by SAS Institute) used in the production of NZDep2018. Clare Salmond (BSc (Hons); MSc) is a former member of the Department of Public Health, University of Otago, Wellington. Clare retired from her position as Senior Lecturer in Biostatistics in that Department in 2004, but has maintained her active association with the NZDep project. Clare has thirty-five years’ experience working as a biostatistician at the Wellington Hospital Epidemiology Unit and at the University of Otago (in both Dunedin and Wellington). She has published extensively in the epidemiology and medical research literature. Peter Crampton (CNZM; MB ChB; PhD; MPH; FNZCPHM; FRNZCGP) is Professor of Public Health in Kōhatu, Centre for Hauora Māori, University of Otago, Dunedin. Peter is a specialist in public health medicine. His research is focused on social indicators and social epidemiology, health care policy, and primary health care organisation and funding. He has taught undergraduate and postgraduate courses related to public health, health systems and health services management. 6 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington Acknowledgements The original NZDep91 project, on which NZDep96, NZDep2001, NZDep2006, NZDep2013 and NZDep2018 are based, was carried out at the Health Services Research Centre at Victoria University of Wellington and was funded by the Health Research Council of New Zealand. We are grateful to the Health Services Research Centre for supporting this work, originally, and to the Ministry of Health for supporting the production of NZDep2001, NZDep2006, NZDep2013 and NZDep2018. Equally important has been the tremendous and consistent support that Statistics New Zealand has provided. While the contents of this report have benefited considerably from the assistance of colleagues, the responsibility for this report remains solely with the authors. Ethics and confidentiality Ethical approval for the original NZDep91 project was obtained in May 1995 from the Central Regional Health Authority Wellington Ethics Committee. Access to the data used in this study was provided by Statistics New Zealand under conditions designed to give effect to the security and confidentiality provisions of the Statistics Act 1975. The results presented in this study are the work of the authors, not Statistics New Zealand. 7 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington Executive Summary NZDep2018 is an updated version of the NZDep91, NZDep96, NZDep2001, NZDep2006 and NZDep2013 indexes of socioeconomic deprivation. NZDep2018 combines nine variables from the 2018 census which reflect eight dimensions of deprivation. NZDep2018 provides a deprivation score for each Statistical Area 1, and its constituent meshblocks, in New Zealand. Meshblocks are the smallest geographical units defined by Statistics New Zealand. They are the building blocks for their new small geographical areas, called Statistical Area 1 [SA1], which generally contain between 100 and 200 people. These new areas, and sometimes combinations of them, were used as the basis from which NZDep2018 was calculated. The NZDep2018 index of deprivation has two forms—an ordinal scale and a continuous score. The NZDep2018 index of deprivation ordinal scale ranges from 1 to 10, where 1 represents the areas with the least deprived scores and 10 the areas with the most deprived scores. The NZDep2018 index of deprivation interval variable is the first principal component score, which has been scaled to have mean 1000 index points and standard deviation 100 index points. The NZDep2018 10-point scale is derived from this interval variable. The NZDep2018 scale of deprivation from 1 to 10 divides New Zealand into tenths of the distribution of the first principal component scores. For example, a value of 10 indicates that the meshblock or SA1 is in the most deprived 10 percent of our small areas in New Zealand, according to the NZDep2018 scores. 8 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington It should be noted that NZDep2018 deprivation scores apply to areas rather than individual people. NZDep2018 combines the following census data (calculated as proportions for each small area): Dimension of deprivation Description of variable (in order of decreasing weight in the index) Communication People with no access to the Internet at home Income People aged 18-64 receiving a means tested benefit Income People living in equivalised* households with income below an income threshold Employment People aged 18-64 unemployed Qualifications People aged 18-64 without any qualifications Owned home People not living in own home Support People aged <65 living in a single parent family Living space People living in equivalised* households below a bedroom occupancy threshold Living condition People living in dwellings that are always damp and/or always have mould greater than A4 size *Equivalisation: methods used to control for household composition. 9 NZDep2018 Index of Deprivation (December 2019) Department of Public Health, University of Otago, Wellington Why is this an interim report? In order to preserve the confidentiality of individuals’ information,