If we take recent income per capita estimates at face value, they imply that the average medieval European was at least five times ‘better off’ than the average Congolese today. This raises important questions regarding the meaning and applicability of national income estimates throughout time and space, and their use in the analysis of global economic history over the long term. This article asks whether national income estimates have a historical and geographical specificity that renders the ‘data’ increasingly unsuitable and misleading when assessed outside a specific time and place. Taking the concept of ‘reciprocal comparison’ as a starting point, it further questions whether national income estimates make sense in pre-and post-industrial societies, in decentralized societies, and in polities outside the temperate zone. One of the major challenges in global history is Eurocentrism. Resisting the temptation to compare the world according to the most conventional development measure might be a recommended step in overcoming this bias.