Statistics on African economic growth are widely known to be inaccurate, but the extent and nature of these inaccuracies and their implications for the users of the data have not been rigorously assessed. This article investigates measurement issues of economic growth in post-colonial Tanzania. It is shown here that conclusions on Tanzania's development performance are conditioned by selection of the source of growth evidence. The article argues for an agnostic perspective on Tanzanian economic growth. Modelling efforts of African growth are more sophisticated than the quality of the data justifies. The policy implications are clear. For producers, there needs to be stronger investment into data collection in African economies, and for users, greater caution utilised in quantitative macro studies.