The question of whether to carry out a quinquennial census is being faced by national
statistical offices in increasingly many countries, including Canada, Nigeria, Ireland,
Australia, and South Africa. The authors describe uses, and limitations, of cost-benefit
analysis for this decision problem in the case of the 2016 census of South Africa. The
government of South Africa needed to decide whether to conduct a 2016 census or to rely
on increasingly inaccurate post-censal estimates accounting for births, deaths, and
migration since the previous (2011) census. The cost-benefit analysis compared predicted
costs of the 2016 census to the benefits from improved allocation of intergovernmental
revenue, which was considered by the government to be a critical use of the 2016 census,
although not the only important benefit. Without the 2016 census, allocations would be
based on population estimates. Accuracy of the post-censal estimates was estimated from
the performance of past estimates, and the hypothetical expected reduction in errors in
allocation due to the 2016 census was estimated. A loss function was introduced to
quantify the improvement in allocation. With this evidence, the government was able to
decide not to conduct the 2016 census, but instead to improve data and capacity for
producing post-censal estimates.