Census data ‘unfit for purpose’ – experts

Data compiled in South Africa’s Census 2022 is “unfit for purpose” and should only be used with “extreme caution in planning and resource allocation until thorough investigations” are carried out by Statistics SA, two leading demographic researchers say.

In an article in The Conversation, Tom Moultrie, professor of demography at the University of Cape Town, and Rob Dorrington, professor emeritus at the University of Cape Town, described Census 2022 as setting “an undesirable record – the highest “undercount” on a national survey yet recorded by the United Nations Population Division.

“The reported undercount of 31% is some 10 percentage points higher than the previous highest notified undercount [in Comoros in 2017].”

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Although the 2022 results, released in October last year, were adjusted for the undercount, “it means the results are more estimates than counts, producing a number of anomalies in the census data.

These call their usefulness into question”, the researchers wrote.

Among the factors contributing to the undercount were:

• Attempting to run a census in the middle of the Covid pandemic’s complicated operations. “This decision appears to have been forced by the national Treasury’s refusal to allow the budget for the census to be held over to the next fiscal year.”

• Delays in recruiting and training field staff to conduct in-person data collection.

• Repeated extensions of the period for data collection.

Importance of accurate information

The researchers said that a census is, primarily, as accurate a count as possible of the number of people in a country at a point in time.

It attempts to describe the demographic and socioeconomic characteristics of the population. It also provides key benchmark estimates of fertility and mortality of the population.”

“Census data are also crucial for planning investment and in determining the allocation of resources by both public and private sector entities.

“In particular, a census provides information about small area populations usually not available from other sources. Decisions on where to build houses, schools, infrastructure and factories are shaped by census data.”

Census data is also used as a sampling frame in other surveys, including the Quarterly Labour Force Survey, national poverty lines and burden of disease studies.

“These surveys provide more detailed information on the population, track the progress made in addressing socioeconomic disparities and provide the denominators for a large number of indicators used to track the sustainable development goals.”

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Moultrie and Dorrington described themselves as “demographers with long experience in the analysis of census data from many countries, but particularly with data from every post-apartheid census”.

They said that in a recent technical report published by the SA Medical Research Council, they highlighted a number of operational and logistical difficulties encountered in planning and running SA’s 2022 census.

The said a Post-Enumeration Survey conducted in the second half of 2022 by Statistics SA estimates that the census undercounted the population by 31%.

“Based on demographic reconstruction, the national population of 62 million, after adjustment for the estimated undercount, might have been overestimated by around one million people (or under 2%).

“Half of this excess is attributable to overestimates of the Indian/Asian and white population groups. The estimated undercount in both groups exceeded 60%. The excess is concentrated in those aged 50 and over. It can not plausibly be attributed to net immigration at these ages.”

There “is a significant undercount, even after adjustment, of children aged five at their last birthday,” they said.

Anomalies in estimates

There were a number of anomalies in the national and provincial population estimates by age, sex and population group that are inconsistent with data from previous censuses and national vital registration data.

“The estimates of population numbers at district and municipal levels are highly inconsistent with estimates from a number of other data sources. These include Statistics SA’s own midyear population estimates and data from the voters’ roll from the local government elections.”

They added: “Taken together, these findings call into question the reliability of the 2022 census data as a source for planning and resource allocation, in particular the equitable share formulae.

“These are used by the national Treasury to determine apportionment of budgets to provinces, districts and municipalities.”

They suggested that a thorough investigation should be done by Stats SA, adding that this would require the release of census data collected on fertility, mortality and migration.

Because another census “is unlikely to be held before 2031”, the researchers said “an alternative set of population estimates by age, sex and population group is urgently required as “a better basis for resource allocation and planning”.