Volume 2

Contents

1. An analysis of Job Mobility and Earnings in New Zealand Using Linked Employee-Employer Data
2. Impacts of global recoding to preserve confidentiality on information loss and statistical validity of subsequent data analysis
3. Optimising confidentiality in administrative data tabular data: a comparison of methods and techniques
4. Investigation of the noise method for confidentiality protection of outputs
5. Can the ICD based Injury Severity Scores (ICISS) (on which NZ Injury Prevention Strategy official statistical indicators are based) be improved?
6. Utilisation of Official Statistics in the Auckland Region
7. Investigation of User Requirements to Improve Wage Measures

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1. An analysis of Job Mobility and Earnings in New Zealand Using Linked Employee-Employer Data (PDF, 209KB)
Tim Maloney

Abstract: The movement of workers between jobs may play an important role in determining both the average level and overall dispersion in earnings in an economy. Yet, there has been almost no research to date on the extent and nature of job mobility and its possible consequences for individual earnings in New Zealand.

This study provides some initial empirical results on this topic using administrative data provided by Statistics New Zealand (Linked Employee-Employer Data). These data allow us to follow the employment and earnings histories of nearly all employed individuals since April 1999.

Keywords: Job Mobility; Earning; Linked Employee-Employer Data; translation of employees; labour market; administrative data; official statistics; wage rate adjustment.

2. Impacts of global recoding to preserve confidentiality on information loss and statistical validity of subsequent data analysis (PDF, 1350KB)
L. Fraser Jackson, Alistair Gray

Abstract: This project is a first stage in a large research agenda. Previous research has shown the necessity of having table cells with average cell numbers of the order of 5 or more to avoid occurrence of unique or sensitive cells. For many data sets this can assisted by aggregating categories (a global recoding). Using such recodes is the universal practise in statistical agencies, but little attention has been paid to the quantitative magnitude of their effects and to devising recodes which will have the least impact on observable associations within the data.

Basic theoretical conditions for collapsing variables have been known for thirty years. It is essential to improve our empirical understanding of their effects since in practise the conditions are never met perfectly. The objective of the project is to provide guidance in constructing recodes when they are necessary to preserve confidentiality or for other reasons.

Keywords: Confidentiality; information loss; global recoding; statistical validity; official statistics; constructing recodes.

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3. Optimising confidentiality in administrative data tabular data: a comparison of methods and techniques (PDF 673KB)
Dr Michael Slyuzberg, Jarrod Irving, Graeme Buckley (et al)

Abstract: The project is focused on the protection of confidentiality in administrative tabular data. The project team has identified statistical techniques that can be used to identify confidentiality risks in the IR environment. Then it has identified and recommended information loss measures for tabular data that can be used to assess the impact of applying methods of confidentiality protection.

Selected confidentiality protection methods have been compared in an experimental manner and, finally, a list of practical recommendations have been developed to support the process of selecting the most effective method of confidentiality protection in specific situations.

Keywords: confidentiality; official statistics; administrative tabular data.

4. Investigation of the noise method for confidentiality protection of outputs (PDF, 271KB)
James Enright, Shane Vultich, David Law

Abstract: Confidentiality at Statistics New Zealand is a high priority issue. Continual research is carried out to find new confidentiality methods that can be applied to make more data available, and new methods that make data easier to produce.

In tabular magnitude output, one of the more time consuming aspects is applying cell suppression to sensitive cells. A possible alternative to cell suppression is applying "noise" to the underlying data. This project is assessing the appropriateness of the application of noise to unit record data so that sensitive data can be included in summary statistics without breaching confidentiality.

Keywords: noise method; confidentiality; protection of outputs; official statistics; cell suppression.

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5. Can the ICD based Injury Severity Scores (ICISS) (on which NZ Injury Prevention Strategy official statistical indicators are based) be improved? (PDF, 211KB)
Gabrielle Davie, Colin Cryer, John Langley, Daniel Russell

Abstract: Many Government agencies are using statistics to measure their performance in the reduction of injury over time. Statistics NZ is also in the process of establishing a new programme of injury statistics. Research suggests that the indicators that most Government departments are currently using to monitor trends in non-fatal injury are potentially misleading because of their inability to remove service-provision and –access effects from the underlying trend data. Langley J, Stephenson S, Cryer C. Measuring road traffic safety performance: monitoring trends in nonfatal injury. Traffic Injury Prevention 2003: 4: 291-296

Valid measurement of injury severity is critical to producing valid indicators, as well as for the production of valid information from the analysis of injury data to inform policy and injury prevention practice. This project aims to investigate improvement in the measurement of injury severity using an enhancement of the International Classification of Disease (ICD)-based Injury Severity Score (ICISS).

ICISS is a threat-to-life severity score that can be calculated from routinely collected data. This project will address the questions, can the predictive ability of ICISS be enhanced through the use of integrated hospitalisation and mortality data sources to calculate ICISS scores and does taking account of comorbidity improve the predictive ability of the ICISS scores?

Logistic regression models using ICISS as the predictor variable and survival as the outcome variable will be used to assess the performance of the ICISS severity scores. The models will be assessed in terms of their discrimination and calibration. The main outcome of this project would be either the production of a more valid measurement of injury severity or the assurance that the currently used method of injury severity measurement is satisfactory.

Answering the two aims of this research will enable the production of more trustworthy injury statistics for the purposes of measuring the impact of policy and practice in reducing injury in New Zealand.

Keywords: Injury Severity Scores (ICISS); official statistics; NZ Injury Prevention.

6. Utilisation of Official Statistics in the Auckland Region (PDF, 744KB)
Charles Crothers, Alex Woodley, Tom Davies

Abstract: The conceptual approach adopted is a comparative organisational study of information and knowledge which would seek to trace the (spatial and temporal) pathways of official social and economic statistics from data-collection, processing and aggregation, into the different phases of utilisation in particular user organisations.

Empirically, the study would investigate very carefully the conceptual and logistical frameworks within which various user communities in the Auckland region visualise and use official statistics and other related information sources. By relating their statistical practises to their goals and aspirations, the study would also derive an understanding of what their data needs are.

The minimum design is to interview an adequate (but small) sample of people at several layers of each of 4-5 of the 7 TLAs in the Auckland region and also the ARC, with a subsequent research interest in rounding out the regional ‘statistical’ picture by later extending the project to DHBs, Auckland regional offices of Ministries, Commercial and Voluntary sector users.

Keywords: statistical practices; official social and economic statistics; data-collection; utilisation of official statistics.

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7. Investigation of User Requirements to Improve Wage Measures (PDF, 255KB)
Dr Adolf Stroombergen

Abstract: This project is intended to research and assess user requirements to improve understanding and utilisation of wage measures and where appropriate to propose a wider, enhanced series of wage measures for short and long term action. This project ultimately aims to improve the quality and effectiveness of wage measures to ensure user confidence and to guarantee the continued relevance of these outputs in policy and decision making.

Keywords: Wage measures; policy and decision making; user requirements; official statistics.

Disclaimer

Official Statistics Research, through Statistics New Zealand, commissioned these reports. The opinions, findings, recommendations and conclusions expressed in the reports are those of the author(s), do not necessarily represent Statistics New Zealand and should not be reported as those of Statistics New Zealand. The department takes no responsibility for any omissions or errors in the information contained in these reports.