Nigeria’s recent population censuses: a Benford-Theoretic Evaluation
Population studies
32
Issue: 1
(02 - 2018)
Context: Population censuses in Nigeria have been plagued with under- or over-enumeration,
as well as outright manipulation. This paper examines the claim of manipulated results of
Nigeria’s 1991 and 2006 population censuses.
Data Source & Method: Data on both censuses were obtained from the National Bureau of
Statistics and analyzed via fitting Benford’s probability distribution. The overall census data, as
well as aggregate data for the six geopolitical zones of the country were examined to
determine the level of conformity with Benford’s distribution, using the Chi-square goodness of
fit test.
Findings: The conformity analyses showed that the overall counts differed significantly from
Benford's in both censuses. The North-West region had the highest deviation in both
censuses, while the North-East and South-West had the lowest deviation in 1991 and 2006
censuses, respectively. Significant conformity was observed in the sizes of the local
government areas and the population density for the 2006 census.
Conclusion: Some datasets with built-in minimum and maximum values may still conform to
Benford’s distribution provided the range of values of the first significant digit span digits 1 to 9.
Census results should be scrutinized on the basis of Benford’s distribution as an additional
check on the quality.
Keywords: Benford’s distribution; demography; population census; fraud-detection.
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