National censuses collect, classify and tabulate vast quantities of personal data on a regular basis. The resultant numerical tables require analysis and interpretation. It has been the census superintendents, charged with the collection and processing of the data, who made the first comments on their work. Their reports provide guides for users seeking to make sense of the complex numerical tabulations. An examination of the reports on the censuses of Sri Lanka demonstrates the evolution of the census superintendents’ approaches to the collection and presentation of data on ethnicity, religion and language. The classification schemes developed in the early colonial censuses have been retained, with modifications, until the present. Continuity and change are documented in the official commentaries, which have acted as guides to make the results, and the reasoning behind them, more accessible to those who not only filled in the questionnaires, but also used the statistics.