2006 Post-enumeration Survey

Note: refer to 'A Report on the 2006 Post-enumeration Survey' for in depth information on the 2006 PES linked in this series. The 2006 PES was based on a stratified, multi-stage sample of 10,900 permanent private dwellings. The survey population consisted of New Zealand residents, either usually resident in a New Zealand private dwelling, or staying at one during the survey period. For the first time, in 2006 overseas visitors who were resident in a private dwelling at the time of the PES and were somewhere in New Zealand on census night, were also included. Overseas visitors were surveyed to investigate the consistency of identification of person type (resident or overseas visitor) between the census and the PES. For practical reasons, n on-private and other private dwellings were excluded from the survey, as were dwellings in remote areas. T he survey period was chosen to avoid overlap of census enumerators and PES interviewers in the field, while being close enough to census date (7 March) to assist respondent recall. Matching was done to determine if a PES respondent was counted in the census at each address at which they stated that they had completed a census form, or at each address where a census form may have been completed for them (search address). This was achieved by comparing the information given by PES respondents with the information given on census forms. If an address given was different to the PES address, searching was carried out to locate the address. Data collected in the PES is used to estimate census coverage for both people and private dwellings. The n et undercount estimates produced from the PES are subject to both sampling and non-sampling errors. The estimation methodology for the 2006 PES includes several improvements over that used in 2001 and 1996. This change in methodology has had some impact on the comparability of undercount estimates between 2006 and earlier PESs. Essentially, the 2006 methodology has reduced bias at the expense of some increase in sampling error. The main changes are: Not all people responding in the PES are eligible to be included in the estimation formula. In 1996 and 2001, the estimation methodology incorporated special procedures for census forms received after PES interviews had started. In 2006, difficulties with the census field management system meant that the number of census late returns was unable to be accurately determined (that is, we could not always identify whether a census form was returned late or on time). The information collected from the PES sample is combined using weights to provide an estimated undercount for the whole population. In 2001, a person’s ‘weight’ was determined initially by their probability of selection into the PES sample, and then adjusted to account for non-response in the sample. Prior to the 2006 PES, estimates of sampling error were calculated using an approximate analytical formula. The changes to the weight adjustment methodology and standardisation of methods for calculating sampling errors within Statistics NZ has meant that the 2006 PES sampling errors are calculated using a replicated sampling technique. en-NZ