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.