Post-enumeration Survey (PES) - Statistics South Africa

Statistics South Africa
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Usually more people are missed than over-counted during a census, so the census count of the
population is lower than the true population. This difference is called net undercount. Rates of net
undercount can vary significantly for different population groups depending on factors such as sex, age
and geographic location. Stats SA obtains estimates of net undercount using information collected
through a Post-enumeration Survey (PES). A PES is a special survey undertaken shortly after the
census to evaluate the completeness of census coverage. It provides a concrete statistical basis for
estimating census coverage, that is, the extent of undercount or overcount, and for adjusting the census
data if there is evidence of significant coverage error. Stats SA used the PES to evaluate census
coverage for Census '96 and Census 2001. Stats SA once again used the PES to evaluate the coverage
of Census 2011. The PES was conducted in approximately 600 enumeration areas (EAs) from
November to December 2011.
1.2 Objectives of the Post-enumeration Survey
The main goal of the PES was to evaluate the quality of census data by collecting high-quality data
immediately after the completion of census enumeration. The specific objectives of the PES project were
as follows:
• to evaluate the accuracy of census data by providing quantitative information on coverage and
content error at specified levels of estimation; national, provincial and geography type (urban and
non-urban);
• to provide stakeholders with quantitative information to enable determination of the overall success
of the census programme;
• to identify procedural issues which require improvement in future censuses, particularly if sources
and causes of errors are identified;
• to evaluate the quality of census enumeration area (EA) maps as sampling units for inter-census
and household-based surveys; and
• to provide statistical basis for adjustments of census data, if and when it becomes necessary.
1.3 Planning of the PES
The PES was an integral part of the Census 2011 programme. For purposes of implementing the PES,
which is supposed to be independent from the census, Statistics South Africa's Methodology and
Evaluation division was mandated with managing the organisation and fieldwork operations of the PES.
Planning included the drafting of strategic and operational plans for the Census 2011 PES. These
documents stated the purpose of the PES, timelines of the project, as well as resource requirements
(financial, human and otherwise). The schedule of activities for the PES were synchronised with census
activities. The determination of timelines also took into account the fact that international best practices
recommend that the PES should be conducted within a closed population, i.e. it should be carried out
within a few months, preferably within six (6) months, after the completion of census fieldwork to ensure
that the impact of natural population changes, such as births, deaths and migration, as well as
Post Enumeration Survey (PES)