Crime Victimisation, Australia methodology

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Reference period
2019-20 financial year
Released
18/02/2021

Overview

This publication contains results from the Crime Victimisation Survey (CVS), a topic on the Multipurpose Household Survey (MPHS) conducted throughout Australia from July 2019 to June 2020. The MPHS, undertaken each financial year by the Australian Bureau of Statistics (ABS), is a supplement to the monthly Labour Force Survey (LFS) and is designed to collect statistics for a number of small, self-contained topics.

The survey collected details about the prevalence of a selected range of personal and household crimes, including the socio-demographic characteristics of persons experiencing the selected crimes, experiences of repeat victimisation, and the characteristics of the most recent incident of each crime type experienced. Some estimates from previous iterations of the survey are also included in this publication. Labour force characteristics, education, income and other demographics was also collected.

Data collection

Scope

The scope of the survey was restricted to people aged 15 years and over who were usual residents of private dwellings and excludes:

  • members of the Australian permanent defence forces
  • certain diplomatic personnel of overseas governments, customarily excluded from Census and estimated resident population counts
  • overseas residents in Australia
  • members of non-Australian defence forces (and their dependants)
  • persons living in non-private dwellings such as hotels, university residences, boarding schools, hospitals, nursing homes, homes for people with disabilities, and prisons
  • persons resident in the Indigenous Community Strata (ICS).

The scope for MPHS included households residing in urban, rural, remote and very remote parts of Australia, except the ICS.

Coverage

In the LFS, rules are applied which aim to ensure that each person in coverage is associated with only one dwelling, and hence has only one chance of selection in the survey. See Labour Force, Australia for more detail.

Collection method

The survey is one of a number of small, self-contained topics on the MPHS.

Each month, one eighth of the dwellings in the LFS sample were rotated out of the survey and selected for the MPHS. After the LFS had been fully completed for each person in scope and coverage, a usual resident aged 15 years or over was selected at random (based on a computer algorithm) and asked the additional MPHS questions in a personal interview. 

In the MPHS, if the randomly selected person was aged 15 to 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 questions on behalf of the 15 to 17 year old (proxy interview). Questions relating to sexual assault and the involvement of alcohol or substances in the most recent incident of physical assault and face-to-face threatened assault were not asked of proxy respondents or persons aged 15 to 17 years.

Data were collected using Computer Assisted Interviewing (CAI), whereby responses were recorded directly onto an electronic questionnaire in a notebook computer, with interviews conducted either face-to-face or over the telephone. The majority of interviews were conducted over the telephone.

Sample size

After taking into account sample loss, the response rate for the 2019-20 survey was 76.4%. In total, information was collected from 29,793 fully responding persons. This includes 494 proxy interviews for people aged 15 to 17 years, where permission was not given by a parent or guardian for a personal interview.

Data processing

Weighting

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 enumerated person. The weight is a value which indicates the number of persons in the population represented by the sample person.

The first step in calculating weights for each unit is 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 (that is, they represent 600 people).

    Benchmarks

    The initial weights were calibrated to align with independent estimates of the population of interest, referred to as 'benchmarks'. 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.

    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.

    The survey was benchmarked to the Estimated Resident Population (ERP) living in private dwellings in each state and territory at December 2019. People living in Indigenous communities were excluded. These benchmarks are based on the 2016 Census.

    While LFS benchmarks are revised every 5 years, to take into account the outcome of the 5-yearly rebasing of the ERP following the latest Census, the supplementary surveys and MPHS (from which the statistics in this publication are taken) are not. Small differences will therefore exist between the civilian population aged 15 years and over reflected in the LFS and other labour household surveys estimates, as well as over time. If comparisons are being made over time then proportions should be used rather than estimates of persons.

      Estimation

      Survey estimates of counts of persons are obtained by summing the weights of persons with the characteristic of interest.

        Confidentiality

        To minimise the risk of identifying individuals in aggregate statistics, a technique is used to randomly adjust cell values. This technique is called perturbation. Perturbation involves a small random adjustment of the statistics and is considered the most satisfactory technique for avoiding the release of identifiable statistics while maximising the range of information that can be released. These adjustments have a negligible impact on the underlying pattern of the statistics. After perturbation, a given published cell value will be consistent across all tables. However, adding up cell values to derive a total will not necessarily give the same result as published totals.

        Perturbation has been applied to Crime Victimisation Survey datasets since 2013-14. Data from previous cycles (2008-09 to 2012-13) have not been perturbed, but underwent a different confidentialisation method to protect the confidentiality of respondents.

        Reliability of estimates

        All sample surveys are subject to error which can be broadly categorised as either sampling error or non-sampling error. For more information refer to the Accuracy section.

          Data quality

          Crime victimisation surveys are best suited to measuring crimes against specific individuals or households. Respondents 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.

          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 a person may not be aware cannot be measured effectively through a household survey, for example crimes involving deception. It may also be difficult to obtain information about some crimes, such as sexual offences and assault committed by other household or family members, due to the sensitivity of the crime and an increased reluctance to disclose. Some of these crimes may not be fully represented in the data collected. Household survey data exclude crimes against commercial establishments or government agencies.

          This survey covered only selected types of personal and household crimes and does not represent all crime in Australia. Personal crimes covered in the survey were physical assault, threatened assault (face-to-face and non-face-to-face), robbery and sexual assault. Household crimes covered were break-in, attempted break-in, motor vehicle theft, theft from a motor vehicle, malicious property damage and other theft.

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

          Experiences of family and domestic violence

          There is limited information available in this publication about family and domestic violence. The Crime Victimisation Survey collects information about experiences of personal violence and the relationship between the victim and perpetrator, however this information alone is not sufficient to reliably measure the number of people who have experienced family and domestic violence.

          The Crime Victimisation Survey collects incident characteristics information, including relationship to the perpetrator, only for the most recent incident of each type of personal crime experienced in the 12 months prior to interview. This means that not all experiences of personal violence by each relationship type - including current and previous partners - are captured in the survey. In addition, as interviews are conducted by telephone in the respondent’s home, there is no requirement for a private interview setting for the Crime Victimisation Survey (as is the case for the ABS’s Personal Safety Survey). This non-private setting means respondents may be less likely to disclose any experiences of violence by their partner if their partner is present in the home at the time of interview. As a result, the statistics on relationship type available in this publication cannot be used to draw conclusions about the prevalence of family and domestic violence in Australia.

          Due to the ongoing relationship between victim and perpetrator, family and domestic violence is often a recurring event, and the protracted nature of this violence cannot be reliably measured within the framework of the Crime Victimisation Survey. Further information about defining and measuring family and domestic violence is available in Defining the Data Challenge for Family Domestic and Sexual Violence and statistics are available in Personal Safety, AustraliaDirectory of Family, Domestic, and Sexual Violence Statistics, 2018, and Recorded Crime - Victims, Australia.

          Statistical measures of crime victimisation

          The level of victimisation can be measured and expressed in more than one way. The most common measure derived from crime victimisation surveys is prevalence, that is, the number of the relevant population that have experienced a given crime at least once in the reference period. Victimisation rates used in this publication represent the prevalence of selected crimes in Australia, and are expressed as a percentage of the total relevant population. Reporting rates used in this publication are expressed as the percentage of persons/households whose most recent incident of each type of crime had been reported to the police.

          Other methodological issues

          When interpreting data from this survey, consideration should be given to the representativeness of the survey sample in relation to the entire in-scope population. This is affected by the response rate and scope and coverage rules. For example, people living in boarding houses, refuges or on the streets are excluded from this survey and may experience different levels of victimisation than those surveyed who live in private dwellings.

          Classifications

          Country of birth

          Education

          Equivalised weekly household income

          Socio-economic Indexes for Areas (SEIFA)

          Comparing the data

          Comparability of time series

          As a similar methodology has been adopted for the surveys, data on the prevalence of personal and household crimes is comparable across the survey periods. This has enabled some time series comparisons to be made in this publication.

          Comparability with police statistics

          Data for selected crimes reported to and recorded by police agencies in a calendar year are available in Recorded Crime - Victims, Australia. 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 experiences of repeat victimisation. The information from the survey should be viewed as complementary to police recorded crime statistics.

          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 the behaviours they experienced. The definitions of terms used in the publication are based on the wording of the questions asked of the respondent and specifications provided to interviewers. Definitions of crime types included in this survey can be found in the Glossary.

          The Crime Victimisation Survey collects information on crimes that were reported to police, as well as crimes that went unreported. In this publication, reporting rates are based on whether or not the most recent incident of each crime type experienced in the 12 months prior to interview was reported to police. Interviews were conducted over a 12 month period from 1 July 2019 to 30 June 2020. The actual reference period for a particular respondent was determined by the date of their interview. There is no way of verifying that a crime was reported to police, where the respondent indicated that police were informed.

          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 (face-to-face and non-face-to-face), and robbery for all persons aged 15 years and over, and sexual assault for persons aged 18 years and over. In contrast, police statistics include victims of all ages, and any comparisons should take this into consideration. Furthermore, police statistics for a given reference period may include criminal incidents that came to the attention of police during the reference period, but did not occur during it.

          Due to differences between collections, caution should be exercised when comparing data from surveys and administrative by-product collections that relate to crime and justice topics. For more information on comparisons between sources, please refer to Measuring Victims of Crime: A Guide to Using Administrative and Survey data, June 2011.

          Comparability to monthly LFS statistics

          Since the survey is conducted as a supplement to the LFS, data items collected in the LFS are also available in this publication. However, there are some important differences between the two surveys. The LFS had a response rate of over 90% compared to the MPHS response rate of 76.4%. The scope of the Crime Victimisation Survey and the LFS also differ (refer to these sections above). Due to the differences between the samples, data from this survey and the LFS are weighted separately. Differences may therefore be found in the estimates for those data items collected in the LFS and published as part of the Crime Victimisation Survey.

          Comparability with other ABS surveys

          Caution should be taken when comparing across ABS surveys and with administrative by-product data that relate to crime and justice issues. Estimates from the Crime Victimisation Survey may differ from those obtained in other surveys (such as the Personal Safety Survey, National Aboriginal and Torres Strait Islander Health Survey, National Aboriginal and Torres Strait Islander Social Survey, and General Social Survey) due to differences in survey mode, methodology and questionnaire design.

          Data pooling

          This edition of the CVS publication presents, for the first time, pooled data on victimisation and reporting estimates at the state and territory level. Data pooling is a statistical technique in which data from multiple survey cycles are combined together to produce more reliable estimates. This effectively increases the sample size of the data set and allows for the production of more robust estimates by decreasing the associated sampling error. For the CVS, this has particular utility for improving the reliability of estimates for less populous states and territories, and lower prevalence crime types such as robbery and sexual assault. The pooled data have been provided in addition to the existing time series estimates and can be found in Tables 28-33.

          The pooled estimates in this release were derived by combining data from consecutive CVS reference periods (survey cycles) and dividing the weights by the number of cycles that were pooled.  The estimates therefore do not correspond to one particular survey cycle but instead are an average of the estimates over the pooled reference period. Two-year pooled estimates were deemed suitable for the majority of personal and household crimes. In the case of sexual assault however, three survey iterations were required to produce meaningful estimates at the jurisdiction level, due to the relatively low prevalence of this crime in Australia.

          CVS data have been pooled based on an assessment of the survey’s comparability and consistency over cycles.  Each CVS iteration is conducted on an independent sample of the same population, and the population characteristics and variables of interest have not changed substantially from one survey to the next. Survey questions regarding victimisation and reporting have remained consistent since the first CVS in 2008-09. Successive CVS iterations have also had similar survey design, scope and coverage, enumeration period and weighting method, indicating a high level of conceptual similarity between surveys.

          The pooled reference periods have been labelled according to the survey cycles they are composed of. As such, the 2008-10 pooled period combines data from the 2008-09 and 2009-10 CVS cycles and therefore spans the time interval from July 2008 to June 2010. However, while the pooled estimates draw on data from multiple years, they do not reflect the incidence of violence over the pooled period but instead are based on respondents’ experience of crime over the 12 months prior to interview. For example, the 2018-20 pooled victimisation estimate for physical assault averages the number of persons from the 2018-19 and 2019-20 CVS cycles who reported experiencing physical assault over the last 12 months.

          To provide data users with the greatest amount of flexibility, rolling time series estimates have been provided in the pooled data tables. The rolling estimates combine consecutive periods of a survey so that a survey year can be used in multiple estimates. For example, the 2009-10 CVS cycle has been combined with the 2008-09 cycle to produce the 2008-10 pooled estimate, and with the 2010-11 cycle to produce the 2009-11 estimate. While rolling estimates produce the greatest amount of time points (compared to a non-overlapping approach, in which a survey’s data is used for only one pooled estimate), caution should be used when comparing estimates with overlapping data. These estimates will not be independent due to the overlap in survey years, which can make analysis and interpretation of the data more difficult. The state and territory section of the commentary includes comparisons between the first (2008-10) and last (2018-20) pooled estimates in the time series. Comparisons to the most recent non-overlapping time period (2016-18) are also discussed.

          The estimates in the pooled data tables have not been perturbed, in contrast to estimates in the other publication tables. Instead a different confidentiality measure has been applied and some cells have been suppressed (though included in the totals where applicable), to minimise the risk of identifying individuals. The use of a different confidentiality measure means that some pooled estimates may be higher or lower than both of the previously published single-year estimates that make up the pooled data.

          Data release

          Data cubes/spreadsheets 

          Data cubes containing all tables for this publication in Excel spreadsheet format are available from the Data downloads section of the main publication. The spreadsheets present tables of estimates and proportions, and their corresponding relative standard errors (RSEs).

          As well as the statistics included in this and related publications, the ABS may be able to provide other relevant data on request. Subject to confidentiality and sampling variability constraints, tables can be tailored to individual requirements for a fee. A list of data items from this survey is available from the Data downloads section. All enquiries should be made to the National Information and Referral Service on 1300 135 070, or email client.services@abs.gov.au 

          Accuracy

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          Glossary

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          Abbreviations

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