This study analyses to which extent the classification of countries as developing corresponds with their actual development level. It tracks the evolution of the development status classification schemes (DSCSs) of international organisations over time, identifies three broad concepts of a developing country, based on the social sciences literature, and analyses the degree of correspondence between classifications and concepts, based on eight indicators. The results suggest that development status is a fairly accurate measure of development. All DSCSs strongly correspond with all indicators analysed. Over time, the outcomes of DSCSs have become increasingly heterogeneous. As a result, different classification schemes match different concepts. Schemes of a first generation, which emerged before the 1990s, and which nominate countries for classes, correspond mainly with concepts focusing on difficult starting points or an early stage in systemic transition, whereas schemes of a second generation, set up in the 1990, which classify countries based on specified criteria, typically reflect a welfare-based concept. The paper argues that the growing heterogeneity of DSCSs and deficits in their documentation negatively impact on the quality of international official statistics. It makes proposals for the further development of DSCSs, also in the context of the 2030 Agenda for Sustainable Development.