The goal of the Census is to obtain a complete measure of the number and characteristics of people in Australia on Census Night and their dwellings, but it is inevitable that a small number of people will be missed and some will be counted more than once. In Australia more people are missed from the Census than are counted more than once. The net effect when both factors are taken into account is an undercount.
During the delivery and collection of Census forms to households, quality assurance field procedures are put into practice to ensure the maximum number of households are included in the Census.
Supervisors are responsible for eight to ten Census Collectors. The supervisors' main role is to ensure accuracy and completeness of coverage within their areas. They must take into account any changes in the number and type of dwellings in their area since the completion of Collection District design. They also review each Collector's work, using a defined set of checks of the forms that have been returned. This ensures that all relevant details are recorded in the Collector's record book, and that a form exists where expected.
Every effort is made to ensure that all households receive a Census form and that these are collected and completed. For example, where Census Collectors are not initially successful in collecting a Census form, they are required to return to a household a minimum of three times after Census Night to attempt to collect the form. Collectors are also required to scan questions 1 to 8 of each form to ensure it has been completed.
All forms are registered to the Collection District they come from, so that Data Processing Centre staff can account for all forms received as well as those still to be returned by mail or electronic lodgement (eForms). Ensuring receipt of the expected number of forms for each Collection District from the collection phase is a critical measure of the completeness of the Census, and for processing and final data.
Some groups of people in the population are undercounted in the Census. These include Aboriginal and Torres Strait Islander people, ethnic groups who have trouble reading or speaking English, the homeless and people with certain disabling conditions which prevent them from filling in a Census form. In addition, some areas are more difficult to enumerate, including secure apartment buildings and remote discrete communities. Special strategies have been developed to ensure a more complete count of these groups and areas.
Post Enumeration Survey
A measure of the undercount in the Census is obtained from a sample survey of households undertaken shortly after the Census, called the Post Enumeration Survey. It collects information about where people were on Census Night and their characteristics, which are compared to the actual Census forms. The Post Enumeration Survey for the 2001 Census indicated an undercount of 1.8% in the Census.
Information from the 2001 Post Enumeration Survey was used in planning the collection procedures for the 2006 Census, with the aim of improving the distribution and collection of Census forms in the identified undercounted groups.