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EXPLANATORY NOTES

INTRODUCTION

1 The statistics presented in this release were compiled from data collected in the Australian Bureau of Statistics' (ABS) 2010–11 Multipurpose Household Survey (MPHS). The MPHS is conducted each financial year throughout Australia from July to June as a supplement to the ABS' monthly Labour Force Survey (LFS) and is designed to provide annual statistics for a number of small, self-contained topics.

2 In 2010–11 the topics were:

• Crime victimisation
• Learning and work history
• Cultural participation
• Household use of information technology
• Patient experience
• Barriers and incentives to labour force participation
• Retirement and retirement intentions

SCOPE

6 The scope of the LFS is restricted to people aged 15 years and over and excludes the following:

• members of the permanent defence forces
• certain diplomatic personnel of overseas governments, customarily excluded from census and estimated resident populations
• overseas residents in Australia
• members of non-Australian defence forces (and their dependants).

• people living in very remote parts of Australia
• people living in non-private dwellings such as hotels, university residences, students at boarding schools, patients in hospitals, residents of homes (e.g. retirement homes, homes for persons with disabilities, women's shelters), and inmates of prisons.

DATA COLLECTION

11 The MPHS was conducted as a supplement to the monthly LFS. Each month one eighth of the dwellings in the LFS sample were rotated out of the survey. Genarally, around 80% of these dwellings were then selected for the MPHS each month. In these dwellings, after the LFS had been fully completed for each person in scope and coverage, a person aged 15 years and over was selected at random (based on a computer algorithm) and asked the various MPHS topic questions in a personal interview. If the randomly selected person was aged 15–17 years, permission was sought from a parent or guardian before conducting the interview. If permission was not given, the parent or guardian was asked the crime questions on behalf of the 15–17 year old, but was not asked the questions about perceptions of social disorder, or the questions relating to alcohol or substances contributing to the most recent physical or face-to-face threatened assault. Only those persons aged 18 years and over were asked questions on sexual assault. Data was collected using Computer Assisted Interviewing (CAI), whereby responses were recorded directly onto an electronic questionnaire in a notebook computer, usually during a telephone interview.

12 For the 2010–11 MPHS, the sample was accumulated over a 12 month period from July 2010 to June 2011.

13 The publication Labour Force, Australia (cat. no. 6202.0) contains definitions of demographic and labour force characteristics, and information about telephone interviewing that is relevant to both the monthly LFS and MPHS.

Sample size

14 The sample size may vary for different topics in the MPHS. The initial sample for the crime victimisation topic was 38,660 private dwellings, from which one person was randomly selected. Of the 32,555 private dwellings that remained in the survey after sample loss (for example, dwellings selected in the survey which had no residents in scope for the LFS, vacant or derelict dwellings and dwellings under construction), 26,405 or 81% fully responded to the questions on crime victimisation.

ESTIMATION METHOD

Weighting

15 Weighting is the process of adjusting results from a sample survey to infer results for the total in-scope population. To do this, a 'weight' is allocated to each sample unit, which, for the MPHS can be either a person or a household. The weight is a value which indicates how many population units are represented by the sample unit. For the MPHS, the first step in calculating weights for each unit was to assign an initial weight, which is the inverse of the probability of being selected in the survey. For example, if the probability of a person being selected in the survey was 1 in 600, then the person would have an initial weight of 600 (i.e. they represent 600 people).

Benchmarking

16 The initial weights were then calibrated to align with independent estimates of the population of interest, referred to as 'benchmarks', in designated categories of age by sex by area of usual residence. Weights calibrated against population benchmarks ensure that the survey estimates conform to the independently estimated distribution of the population rather than the distribution within the sample itself. Calibration to population benchmarks helps to compensate for over or under-enumeration of particular categories of persons/households which may occur due to either the random nature of sampling or non-response.

17 For person estimates, the MPHS was benchmarked to the projected population in each state and territory, excluding the population living in very remote areas of Australia, at 31 March 2011. For household estimates, the MPHS was benchmarked to independently calculated estimates of the total number of households in Australia. The MPHS estimates do not (and are not intended to) match estimates for the total Australian person/household populations obtained from other sources (which may include persons living in very remote parts of Australia).

Estimation

18 Survey estimates of counts of persons or households are obtained by summing the weights of persons or households with the characteristic of interest. Estimates of non-person counts (e.g. number of attempted break-ins) are obtained by multiplying the characteristic of interest with the weight of the reporting person/household and then aggregating them.

RELIABILITY OF ESTIMATES

19 All sample surveys are subject to error which can be broadly categorised as either:

• sampling error
• non-sampling error.

DATA QUALITY
INTERPRETATION OF RESULTS

22 Crime victim surveys are best suited to measuring crimes against individuals or households with specific victims. Victims need to be aware of and recall what happened to them and how it happened, as well as be willing to relate what they know to interviewers.

23 Not all types of crime are suitable for measurement by household surveys. No reliable information can be obtained about crimes without specific victims, such as trafficking in narcotics. Crimes of which the victim may not be aware cannot be measured effectively - some crimes involving deception and attempted crimes of many types may fall into this category. It may also be difficult to obtain information about some crimes such as sexual offences and assault committed by other household members due to the sensitivity of the crime and an increased reluctance to disclose. Some of these crimes may not be fully reflected in the data collected. Household survey data excludes crimes against commercial establishments or government agencies.

24 This survey covered only selected types of personal and household crimes. Personal crimes covered in the survey were physical assault, threatened assault, robbery and sexual assault. Household crimes covered were break-ins, attempted break-ins, motor vehicle theft, theft from a motor vehicle, malicious property damage and other theft. The survey also covered people's perceptions about social disorder problems in their local area.

25 For this survey the definition of total victims is restricted to those crimes included in the survey and does not represent all crime in Australia.

26 Information collected in this survey is essentially 'as reported' by respondents and hence may differ from that which might be obtained from other sources or via other methodologies. This factor should be considered when interpreting the estimates and when making comparisons with other data sources.

Statistical measures of crime victimisation

27 The level of victimisation can be expressed in more than one way. The most common measure derived from crime victim surveys is prevalence, that is, the number of the relevant population that have been a victim of a given crime at least once in the reference period. This is known as the 'victimisation rate'. Victimisation rates used in this publication represent the prevalence of selected crimes in Australia, and are generally expressed as a percentage of the total relevant population. Reporting rates used in this publication are expressed as the percentage of victims whose most recent incident of crime had been reported to the police.

DATA COMPARABILITY

28 The 2010–11 Crime Victimisation Survey is the third in a new series of regular Crime Victimisation Surveys conducted by the ABS. The two previous surveys in this series (conducted for the 2008–09 and 2009–10 reference periods) included many of the questions asked in 2010–11. This has enabled some time series comparisons to be made in this publication.

29 The new series was introduced because of a change to the collection methodology. The new method of collection mainly uses personal telephone interviews of selected respondents. Previous data collections since 1990 required respondents to self complete questionnaires and mail these back to the ABS. This difference in mode of collection and changes to survey questions means that data collected using the MPHS is generally not directly comparable with data from previous years' Crime and Safety surveys.

30 Since 1990, Crime and Safety surveys were conducted by the ABS nationally and in specific states and territories at different times. Collections have taken place in the following years:

32 Most of the questions asked in the 2008–09 and 2009–10 Crime Victimisation Surveys have been repeated in 2010–11. As a similar methodology has been adopted for the surveys, data on the prevalence of personal and household crimes should be comparable across the periods.

33 Several questions were added to the Crime Victimisation Survey in 2009–10 and continued in 2010–11 which relate to people's perceptions of social disorder in their neighbourhood. These questions replace those on people's feelings of safety and their perceptions of neighbourhood problems asked in 2008–09. While there is some similarity between the social disorder and neighbourhood problem questions, they should not be compared as there are variations in question wording.

34 In the 2008–09 Crime Victimisation Survey, data was not collected in July and August in New South Wales (to avoid overlap with the April 2008 NSW Crime and Safety Survey). In the 2009–10 and 2010–11 surveys, data was collected for the full 12 months, however this change does not impact on the comparability of the data.

35 A significant change has been made to the Area of usual residence data item as shown in this release. In the 2008–09 and 2009–10 crime victimisation publications, Area of usual residence was classified as State capital cities and Balance of state/territory. The Balance of state/territory category comprised people usually resident in areas outside of the six state capital city Statistical Divisions (as defined in the Australian Standard Geographical Classification, ASGC (cat. no. 1216.0)), including all residents of the Northern Territory (except those in very remote areas) and the Australian Capital Territory. For 2010–11, the State capital cities category has been changed to Capital city and now includes all of the ACT and Darwin Statistical Division, while the Balance of state/territory category now comprises people usually resident in areas outside of the eight capital city Statistical Divisions, excluding all residents in the ACT. The new definitions of Capital city and Balance of state/territory, as published, result in Area of usual residence not being comparable across the surveys. However, comparable classifications are available on request. (See Products and Services section below for further details).

Comparability with police statistics

36 Data for selected crimes recorded by police agencies are available in Recorded Crime - Victims, Australia (cat. no. 4510.0). The Crime Victimisation Survey provides an additional source of data on crime victimisation for the selected crimes, including crime not reported to or detected by police. This survey identifies the nature of this unreported crime, as well as giving information about victims of repeated crimes. The information from the survey should be viewed as a complement to published police statistics on crime.

37 The terms used for the crimes (such as robbery and physical assault) may not necessarily correspond with the legal or police definitions used. This is because responses obtained in this survey are based on the respondent's perception of being the victim of a crime. The definitions of terms used in the survey are based on the wording of the questions asked of the respondent and specifications provided to interviewers. Main definitions can be found in the Glossary.

38 For each crime type, survey respondents were asked how many of the incidents that happened to them in the 12 months prior to the interview became known to the police. As interviews were conducted during 2010–11 the data in this publication relates to crimes occurring over a 12 month period at some time between July 2009 and June 2011. The actual reference period for a particular respondent was determined by the date of their interview. Also, there is no verification a crime report has actually been made for the crime if a survey respondent indicates that police were informed about the incident.

39 Another source of variation between the survey results and crimes recorded by police relates to differences in scope. This survey collects information on the personal crimes of physical assault, threatened assault and robbery for all people aged 15 years and over, and sexual assault for people aged 18 years and over. In contrast, police statistics include victims of all ages and any comparisons need to allow for this difference. Furthermore, police record all crimes reported to them in the reference period, whether or not the incidents took place during that period or at an earlier time.

Comparability with monthly LFS Statistics

40 Due to differences in the scope and sample size of the MPHS and that of the LFS, the estimation procedure may lead to some small variations between labour force estimates from this survey and those obtained from the LFS.

Other methodological issues

41 In the interpretation of the results of the 2010–11 MPHS, consideration should be given to the representativeness of the sample. This is affected by the response rate and also the fact that the survey covers only people living in private dwellings. It does not include people such as the homeless or those living in special accommodation, who may experience different levels of victimisation than others in the community.

CLASSIFICATIONS

42 Country of birth data are classified according to the Standard Australian Classification of Countries (Second Edition) (SACC), 2011 (cat. no. 1269.0).

43 Educational attainment data are classified according to the Australian Standard Classification of Education (ASCED), 2001 (cat. no. 1272.0).

PRODUCTS AND SERVICES

Spreadsheets

44 All tables, in Excel spreadsheet format, can be accessed from Downloads. The spreadsheets present tables of estimates and percents, and their corresponding relative standard errors.

Microdata record file

45 In addition to the data available in the Excel spreadsheets, other tables will be able to be produced using Survey TableBuilder (STB). STB is an online tool for creating tables and graphs from survey data. STB for the 2010–11 Crime Victimisation topic is expected to be available in mid 2012. General information about this product, including cost, can be found on the About Survey TableBuilder page.

46 A Confidentialised Unit Record File for the 2010–11 Crime Victimisation Survey will not be available.

Data available on request

47 A further option for accessing data from the crime victimisation component of the MPHS is to contact the National Information and Referral Service. A range of additional data not provided in the standard spreadsheets may be provided on a fee-for-service basis. A spreadsheet containing a complete list of the data items available from the Crime Victimisation Survey can be accessed from Downloads.

ACKNOWLEDGEMENTS

48 ABS surveys draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated. Without it the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.

RELATED INFORMATION

49 A wide range of information about Crime and Justice statistics can be found on the ABS Crime and Justice Topics @ a Glance web page. This page includes information on current and upcoming projects, links to recent crime and justice publications and resources, and information about current issues in the crime and justice sector.

50 The Related Information tab associated with this release contains links to a selected range of ABS Crime and Justice publications.