Contrary to the classical position, the works of Prebisch and Singer in the middle of the last century launched the controversial hypothesis of a long-term decline in the terms of trade of primary products vis- ́a-vis manufactures and a corresponding decline in the terms of trade of the developing countries vis-a-vis the advanced ones. The present study traces the origin and evolution of the hypothesis and reviews the related statistical debate. It also reviews the theoretical support for the Prebisch-Singer hypothesis. It’s an exercise in the history of economic thought to trace how the controversies surrounding the terms of trade have evolved over time, specifically noting that with the development in the field of econometrics, the central thesis of the argument got somewhere lost in the realm of hi-tech statistical debates.